Evaluate the function - where did I go wrong?

Question

Evaluate the function:
f(x) = x^2 + 5x + 8
at the given values of the independent variable and simplify.

f(x+5) =

My work is as follows:

Fill in the original statement with the given variable:
f(x+5) = (x+5)^2 + 5(x+5) + 8

Evaluate:
f(x+5) = x^2 + 25x + 25 + 5x + 25 + 8

Simplified:
f(x+5) = x^2 + 30x + 58

However, the correct answer was:
f(x+5) = x^2 + 15x + 58

Where did I go wrong and why?

Answer 1

(x + 5)² - x² + 10x + 25 ; this is where your mistake was 

 

f(x + 5) = (x + 5)2 + 5(x + 5) + 8

 

=  x² + 10x + 25 + 5x + 25 + 8

 

= x² + 15x + 58

Answer 2

f(x+5) = (x+5)² + 5(x+5) + 8 = (x² + 10x + 25) + (5x + 25) + 8

 

= x² + (10x + 5x) + (25 + 25 + 8) = x² + 15x + 58