Chapter 5 - Straight Line Graphs

Question 1

What is the formula to calculate the gradient of a line?

Answer 1

m = y2 - y1
———-
x2 - x1

Question 2

How do you write the equation of a straight line?

Answer 2

y = mx + c

m is the gradient
c is the y- intercept when x = 0

It can also be written as ax + by + c = 0

Question 3

How do you find the equation of a line from a known gradient and set of coordinates?

Answer 3

y - y1 = m(x - x1)

or

m = y - y1
———
x - x1

Expand and simplify so y is the subject.

Question 4

What do parallel lines have in common?

Answer 4

They have the same gradient.

Question 5

If a line has the gradient m what would the perpendicular gradient be?

Answer 5

m

It is negatively reciprocated.

Question 6

What is the product of two perpendicular lines?

Answer 6

-1

Question 7

What is the formula to find the distance between two coordinates?

Answer 7

d = /(x2 - x1)^2 + (y2 - y1)^2

Question 8

How do you find the point of intersection between two lines?

Answer 8

Use a simultaneous equation by either substituting the values or eliminating two values that are equal in both equations.

Question 9

When is the linear model appropriate and when is it not?

Answer 9

It is appropriate when the points are close to the straight line.

It is inappropriate the further away from the straight line the points are.

Question 10

What is the linear model used for?

Answer 10

It shows the relationship between two variables eg cost and time.

If appropriate it shows direct proportion.

Question 11

By a graph how can you find the direct proportion equation?

Answer 11

You find the equation of the line.