Question 230938
First evaluate (f*g)(x), then substitute in x=8

Given {{{f(x)=17x^2-6x}}} and {{{g(x)=8x-5}}}, then (f*g)(x)={{{(17x^2-6x)(8x-5)}}}
Perform FOIL
(f*g)(x)={{{(17x^2)(8x) + (17x^2)(-5) + (-6x)(8x) + (-6x)(-5)}}}
(f*g)(x)={{{136x^3-85x^2-28x^2+30x}}}
(f*g)(x)={{{135x^3-113x^2+30x}}}
Now substitute in x=8
(f*g)(8)={{{135(8^3)-113(8^2)+30(8)}}}
(f*g)(8)=135(512)-113(64)+30(8)
(f*g)(8)=69120-7232+240
(f*g)(8)=62136