QRT Flashcards
Multiplying Fractions
a/b x x/y
Multiply numerators together and denominator together
= ax/by
Dividing Fractions
a/b ÷ x/y
Flip the fraction you’re dividing by then multiply
= a/b x y/x = ay/bx
Solving a Proportion
x/5 = 3/4
Cross-multiply
4x = 15
4 = 15/4
(xm)(xn)
=xm+n
xm / xn
=xm-n
(xm)n
xmn
(xn)(yn)
xyn
xn / yn
(x/y)n
Multiplying Polynomials
(x2 + 3x + 4)(x + 5)
Multiply each term in the first polynomial with each term in the second
=x2(x + 5) + 3x(x + 5) + 4(x + 5)
=x3 + 5x2 + 3x2 + 15x + 4x + 20
x3 + 8x2 + 19x + 20
Dividing Polynomials
(2x3 + 13x2 + 11x -16) ÷ (x + 5)
Use long division:
= 2x2 + 3x - 4
Factoring
ax + ay
a(x + y)
Factoring
a2 - b2
Difference of squares:
(a + b)(a - b)
eg 4x2 - 9 = (2x + 3)(2x - 3)
Factoring
a2 + 2ab + b2
Squares of binomials:
(a + b)2
Factoring
a2 -2ab + b2
Squares of binomials
(a - b)2
For all x ≠ ±3,
(3x2 - 11x + 6) / (9 - x2)
- Factorising: denominator - difference of squares -
(9 - x2) = (3 - x)(3 + x)
- Factorising: numerator -
(3x2 - 11x + 6) = (x -3)(3x - 2)
- Factorising numerator for -1:
(x -3)(3x - 2) = (-1)(3 - x)(3x - 2)
- Cancelling (3 - x):
(-3x + 2)/(3 + x)
Unknown in a Denominator
1 + 1/x = 2 - 1/x
Cross multiply:
(x + 1)/x = (2x-1)/x
x2 + x = 2x2 - x
2x2 - x2 = x + x
x2 = 2x
Dividing both sides by x:
x = 2
Unknown In an Exponent
If 8x = 16x-1, x = ?
Since both bases are factors of two, can be reexpressed as powers of two:
(23)x = (24)x-1
3x = 4x - 4
x = 4
Quadratic Formula
‘In terms of’
If a = (b + x)(c + x), what is the value of x in terms of a, b and c
b + x = ac + ax
ax - x = b - ac
x(a - 1) = b - ac
x = (b - ac)/(a - 1)