college algebra word problem

Question

Find f(a + 1).

f(x) = x^² + 7

Answer 1

f(a+1) = (a+1)^2 + 7 = a^2 +2a + 1 + 7 = a^2 +2a + 8

f(a+1) = a^2 +2a + 8

just substitute a+1 everywhere x appeared in the original function