Question

For the equations of two straight lines y = 3x and y = -2x + 1,

(i) which equation represents direct proportion?
Answer(i):...
(ü) Provide a reason for your answer in (i).

Answer 1

y = 3x equation represent direct proportion.

Explanation:

Direct Proportion:

If x value increases then y value also increases. This is called direct variation or y is directly proportional to x.

For y = 3x

x = 1 , then y = 3

x = 2 , then y = 6

So on, here x is increasing then y is also increases.

Hence, y = 3x equation represent direct proportion.

Inverse Proportion:

If x value increases then y value decreases. This is called indirect variation or y is inversely proportional to x.

For y = -2x + 1

x = 1 , then y = -1

x = 2 , then y = -3

So on, here x is increasing then y decreases.

Hence y = -2x + 1 is Indirect variation.