Question

The function f is defined by f(x)=x^2−7.
Find f(5y).

Answer 1

@lolbunny

Answer 2

f(y)=4x5y

Answer 3

Just substitute 5y for x.

25y^2 - 7

Answer 4

so what is the full answer? How does 25y^2-7 become f(y) =4x5y?

Answer 5

f(x) is x^2 - 7

so if you're finding f(5y), then you substitute 5y into the function in place of x:

f(5y) = (5y)^2 - 7

You see? I just replaced x with 5y.

Then you just simpify it:

25y^2 -7

Answer 6

@shadowdragon just ignore that 4x5y crap, since nobody knows what the hell that guy was talking about.