Question

The y-intercept of g(x)=3/5f(5x) is 15.

Which of the following is the y-intercept of f(x) ?
A/ 3
B/9
C/25
D/75

Answer 1

C) 25

Explanation:

A function is scaled vertically by multiplying every function value by the scale factor. For some scale factor k, the function g(x) = k·f(x) is a vertically scaled version of the function f(x).

Here, we are given ...

g(x) = 3/5·f(x)

This means the y-intercept is also scaled:

g(0) = 3/5·f(0)

f(0) = 5/3·g(0) . . . . . multiply by 5/3

f(0) = 5/3·15 = 25

The y-intercept of f(x) is 25.