Question

Subtract b(b^2 + b-7)+5 from 3b^2-8 and
find the value of expression obtained for
b=-3.​

​

Answer 1

$3b^2-8-(b(b^2+b-7))=\\3b^2-8-(b^3+b^2-7b)=\\3b^2-8-b^3-b^2+7b=\\-b^3+2b^2+7b-8\\\\-(-3)^3+2\cdot (-3)^2+7\cdot(-3)-8=27+18-21-8=16$