If f(x) = x^2 − 7x, please help find f(a − 4), and f(a + h)

Evaluate the function for the given values.
If f(x) = x^2 − 7x, find f(a − 4), and f(a + h).

I was stuck at this problem, please help and thank you!

You just replace (a - 4) in every x in the equation

f(a-4) = (a-4)^2 - 7(a-4)
=(a^2 - 8a +16) -7a + 28
= a^2 - 15a + 44

And you can go further
= (a - 11)(a - 4)

Therefore a= 11 and 4

Evaluate the function for the given values.
If f(x) = x^2 - 7x, find f(a - 4), and f(a + h).

f(a - 4)
= (a - 4)[(a - 4) - 7]
= a^2 - 15a + 44

f(a + h)
= (a + h)[(a + h) - 7]
= a(a + 2h - 7) + h(h - 7)

f(a + h) = (a + h)^2 - 7(a + h)

=> a^2 + 2ah + h^2 - 7a - 7h

=> a^2 + (2h - 7)a + h^2 - 7h

To get f(a - 4) we replace h with -4

i.e. a^2 - 15a + 16 + 28

=> a^2 - 15a + 44 = (a - 11)(a - 4)

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