Chapter 5 - Section 5.1 - Introduction to Polynomials and Polynomial Functions - Exercise Set - Page 324: 13

$12$

RECALL: $f(a)$ represents the value of the function $f$ when $x=a$. Thus, $f(-1)$ represents the value of the function $f$ when $x=-1$. Substitute $-1$ to $x$ in the function $f$ to obtain: $f(-1) = (-1)^2-5(-1)+6 \\f(-1)=1-(-5)+6 \\f(-1)=1+5+6 \\f(-1)=12$