To evaluate the expression 7y^2 - 17y + 5 when y = 8, we simply substitute the value of y into the expression and perform the calculations.
Substituting y = 8 into the expression:
7(8)^2 - 17(8) + 5
Simplifying:
7(64) - 136 + 5
448 - 136 + 5
313
Therefore, when y = 8, the expression 7y^2 - 17y + 5 evaluates to 313.