Key methods and terminology Flashcards
What are the factors of a number?
numbers that divide into it
What is the definition of BIDMAS?
B - brackets
I - indices
D - division
M - multiplication
A - addition
S - subtrwction
What does LCM stand for and what is included in this?
- lowest common multiple
- the lowest number that can be divisible by both numbers (to give an integer result)
- What does HCF stand for?
- what is included in this?
- highest common factor
- the biggest number that can divide into the numbers within the question
what are the first 10 prime numbers?
2,3,5,7,11,13,17,19,23,29
what are the first 10 square numbers?
1,4,9,16,25,36,49,64,81,100
What is the area of a triangle?
Area of triangle = 1/2 X base X height
what is the area of a square?
area of square = Base X height
what is the area of a circle?
πr2
what is the area of a trapezium?
area of trapezium = (a + b) X h / 2
what is the formula for compound interest?
A = P(1 + r/n)^nt
where:
A = final amount
P = initial principle balance
r = interest rate
n = number of times interest applied per time period
t = number of time periods
what are rational numbers compared to irrational numbers?
rational numbers can be written as: integers, fractions or terminating/recurring decimals
irrational numbers: they cannot be written as fractions; they are never ending, non repeating decimals.
how to multiply or divide fractions?
multiply: multiply the top and bottom separately to create a result fraction
divide: flip the second fraction and multiply with the first (Keep Flip Change)
How to add or subtract fractions?
find a common denominator and then subtract or add the numerators. The denominator (when they are equal) is not effected
How to write reoccurring decimals as fractions?
1) name the decimal a letter (for this example ‘x’)
2) multiply r by 10 to move the decimal place once
3) repeat this until you have the repetitive part one the left of the decimal place
4) subtract the equal decimals (and versions of r - like 100r - 10r)
5) divide to leave r, and cancel if possible
When estimating, what should you round the numbers to?
1 or 2 significant figures
What are bounds?
When a measurement is rounded to a given unit, the actual measurement can be anything up to half a unit bigger or smaller. These are the upper and lower bounds
What happens when a value is truncated?
When a measurement is truncated to a given unit, the actual measurement can be up to a whole unit bigger but no smaller.
What are the 3 rules of standard form?
1- the front number (before the decimal point) must always be between 1 and 10 (cannot be 10)
2 - the power of 10, n, is how far the decimal place moves
3 - n is positive for big numbers, n is negative for small numbers (it depends on which way the decimal place moves)
How to multiply and divide with standard form?
1) rearrange to put the front numbers and powers of 10 together in the equation
2) multiply or divide the front numbers and use the power rules to multiply or divide the powers of 10
3) make sure the answer is in standard form
how to add and subtract with standard form?
1) make sure the powers of 10 are the same - rewrite if not
2) add or subtract the front numbers
3) convert the answer to standard form if necessary
what are the seven simple rules of powers?
- when multiplying, add the powers
- when dividing, subtract the powers
- when raising one power to another, multiply them
- anything to the power of 1 will be itself
- anything to the power of 0 will be 1
- 1 to any power is 1
- with fractions, apply the power to both the top and bottom
with rules 1 and 2, they only work for powers of the same number
what happens with a negative power?
Negative powers - turn it upside down. This will make the power positive, and so you can then have the flipped numbers to the power of the (new) positive number
what happens with fractional powers?
A fractional power (a/b) is the ‘b’ root of the number provided
for example:
the power 1/2 means square root
the power 1/4 means fourth root
What are two-stage fractional powers?
With fractional powers where the numerator is not 1, split the fraction into a root and a power and do them in that order: root first, then power
for example:
64^(5/6) = sixth root of 64 to the power of 5 = 2^5 = 32
what is D.O.T.S?
- Difference Of Two Squares
what are the 6 rules for manipulating surds?
- root a X root b = root a X b
- root a / root b = root a / b
- root a + root b = DO NOTHING! IT ISN’T root a + b
- (a + root b)^2 = (a + root b) X (a + root b)
- (a + root b) (a - root b) = a^2 - b
- rationalise the denominator
how to rationalise the denominator with surds?
It is when you get rid of the root on the bottom of the fraction:
a / root b = a / root b X rootb / rootb
= a X rootb / b
what are the six steps of solving an equation?
1 - get rid of any fractions
2 - multiply out any brackets
3 - collect all the letter terms on one side, and the number terms on the other
4 - combine all the like terms
5 - divide both sides by the number attached to the letter (you may have to factorise to do this as you may need to divide by the brackets)
6 - if you had the letter to the power of a number, root by that number to end up with a positive/negative result
how to factorise a quadratic?
- rearrange into the format ax^2 + bx + c = 0
- find 2 numbers that multiply to ac and add/subtract to b
- rewrite the equation where bx is replaced by the 2 numbers that you found in step 2 (don’t forget x)
- place these 4 values into a grid and factorise
- factorise to find what each bracket is
- then solve the equation by setting each bracket equal to 0 to see the value of x
How to complete the square?
- rearrange the quadratic into the format ax^2 + bx + c = 0
- write out the initial bracket: (x + b/2)^2
- multiply out the brackets and compare to the original to find out what you need to add or subtract to complete the square
- add or subtract the adjusting number to make it match the original
if a does not equal 1, you need to take out the factor of a first, and then multiply it back in later
how to find the nth term of a linear sequence?
- find the common difference (this tells you what to multiply n by)
- work out what to add or subtract to get to the original sequence using n (for example: 3n = 3,6,9)
- write as one equation
how to find the nth term of a quadratic sequence?
- find the difference between each term
- find the second difference between the first differences
- divide this value by 2 to find what to give the coefficient of n^2
- subtract the n^2 term from the sequence to find the linear sequence
- find the rule for the nth term of the linear sequence and add this to the n^2 term
What is the difference between an arithmetic and geometric sequence?
arithmetic - where you add or subtract the same amount each time
geometric - where you multiply or divide by the same amount each time
What is the fibonacci sequence?
where you add together the two previous terms to find the next term
What happens when you multiply or divide by a negative number with an inequality sign?
YOU MUST FLIP THE INEQUALITY SIGN
How to draw inequalities in a number line?
Use an open circle for greater than or less than, and a coloured in circle for greater than/equal to and less than/equal to
what is the general rule for quadratic inequalities?
if x^2 > a^2 then x > a OR x > -a
if x^2 < a^2 then -a < x < a
What is the method for showing inequalities on a graph?
- convert each inequality to an equation (put an equals in place of inequality sign)
- draw the graph for each equation (if it is > or < then draw a dotted line, but if it is ≥ or ≤ draw a solid line)
- work out which side of the line you want (substitute a point into the inequality to see if it is on the correct side of the line)
- shade the region this gives you
how to solve simultaneous equations by having the same coefficient?
- make the equations have one coefficient of the same letter equal (you may need to multiply or divide on equation)
- subtract the equations (if both are positive or negative) or add the equations (if one is negative and one is positive) to get one letter and coefficient on its own)
- then solve the equation normally to find what one of the values are
- substitute this back into one of the equations to find the other unknown value
How to solve simultaneous equations by substitution when it involves a quadratic?
- rearrange the quadratic equation so that it tells you what one of the unknowns are: y = 3x^2 - 3
- substitute this into the other equation to get a new equation
- rearrange this to get a quadratic equation and solve
- substitute the first value back into one of the equations (pick the easiest)
- then try with the second value in the same equation
- you should have two pairs of answers, and write these clearly, using and to link the pairs
what four thins can be useful when answering a proof question?
- any even number can be written as 2n
- any odd number can be written as 2n + 1
- consecutive numbers can be written as: n, n + 1, n + 2…
- the sum, difference and product of integers is always an integer
How to disprove a statement?
Use an example that the statement does not work for (disproof by counter example)
What does a function do?
Takes an input, processes it and outputs a value
How to evaluate a function?
Put the numbers into the function and find the result
What should you do if you have to combine functions?
fg(x)
- it is a composite function
- composite functions are written as fg(x) which means “do g first, then do f using the result of g”
- to find a composite function, rewritten fg(x) as f(g(x) then replace g(x) with the expression it represents:
Given f(x) = 3 x + 2 and g(x) = x + 5, find fg(x)
= f(g(x)) = f(x+5)
= 3(x+5) + 2
= 3x + 15 + 2
= 3x + 17
How to solve an inverse function?
- an inverse function reverse f(x)
- write out the equation x =f(y)
- rearrange to make y the subject
- finally, replace y with f^-1(x)
What is the formula for a straight line equation and what do the letters represent?
y = mx + c
m = gradient
c = y-intercept
What is the formula for gradient of a line?
change in y / change in x
How to find the midpoint of a straight line?
Add the x-coordinates and divide by 2
Add the y-coordinates and divide by 2
How to use ratios to find coordinates?
- find the difference between the coordinates of two points (A and B)
- Now look at the ratio
- the ratio tells you the third point (C) is a fraction of the way from A to B
- find the fraction of each distance (difference between points)
- now add these to the coordinates of the first point (A) to find C
what is the same about parallel lines?
Their gradients - in the equations y=mx+c, the m will be the same
What is the key fact about perpendicular lines and their gradients?
Their gradients are the negative reciprocal of each other
What is the equation for a circle with the centre (0,0)?
The equation for a circle with centre (0,0) and radius (r) is:
x^2 + y^2 = r^2
If you know the radius, substitute it in for r
What do reciprocal graphs look like?
= 1/x graphs
y = A/x or a y = A
These are all the same basic shape where the two halves of the graphs do not touch and do. it exist for x = 0. They are all symmetrical about the lines y = x and y = -x
what do k^x graphs look like?
y = k^x or y = k^-x
- They are exponential graphs, they are always about the x axis and go through the point (0,1)
- If k > 1, and the power is positive, the graph curves upwards
- if k is between 0 and 1, or the power is negative, the graph is flipped horizontally
- the graphs will start to increase very little and then increase rapidly
what do x^3 graphs look like?
y = ax^3 + bx^2 + cx + d
(b,c,d can be zero)
- cubic graphs have a wiggle in the middle (this can be flat or more pronounced)
- in x^3 it goes up from the bottom left
- in -x^3 it goes down from the top left
What are sin and cos graphs?
y = SIN x
y = COS x
sin graphs - waves (bounce between +1 and -1)
cos graphs - buckets (between +1 and -1)
sin graphs have a peak and a trough
cos graphs start at the top, dip and come back up again
How to solve equations using graphs?
Plot both graphs and see where the graphs cross each other
What is the equation for a translation of a graph on the y-axis?
y = f(x) + a
What is the equation for a translation of a graph on the x-axis?
y = f(x - a)
What is the equation for reflections of a graph?
y = -f(x)
y = f(-x)
Describe the points of a distance-time graph?
- at any point, gradient = speed
- the steeper the graph, the faster it is going
- flat sections are where it has stopped
- if the gradient is negative, it is coming back
Describe the points of a velocity-time graph?
- at any point, gradient = acceleration
- negative slope is deceleration (slowing down)
- flat sections are steady velocity
- area under graph = distance travelled
How to find the average gradient?
- Draw a straight line between the two points (these are given in the question)
- find the gradient of the straight line
How to estimate rate at a given point?
- Draw a tangent that touches the curve at the given point
- the gradient of the tangent is the same as the rate at the chosen point
How to deal with changing ratios?
1) write the ratios as equations
2) turn the ratios into fractions
3) solve the equations simultaneously
example:
The ratio of male to female pupils on a trip is 5:3, four male teachers and nine female tea chefs are going. the ratio of males to females is 4:3. How many female pupils are going?
let m be the number of male pupils and f be the number of female pupils
m:f = 5:3
(m+4);(f+9) = 4:3
m/f = 5/3 and m+4/f+9 = 4/3
3 m = 5f and 3m + 12 = 4f + 36
f = 24
24 female pupils are going on the trip
What is the equation for direct proportion using y and x?
y is directly proportional to x
y = kx
What is the equation for inverse proportion using y and x?
y is inversely proportional to x
y = k/x
What are the golden rules for direct and inverse proportion?
direct proportion: divide for one, then times for all
inverse proportion: times for one, then divide for all