已知,A=3x^2+2x+1,B=2x^3-x^2+3x-7,求：A+B=?3A+2B+?

题目

已知,A=3x^2+2x+1,B=2x^3-x^2+3x-7,求：A+B=?3A+2B+?
今天就要

答案

A+B
=3x^2+2x+1+2x^3-x^2+3x-7
=2x^3+2x^2+5x-6
3A+2B
=3(3x^2+2x+1)+2(2x^3-x^2+3x-7)
=9x^2+6x+3+4x^3-2x^2+6x-14
=4x^3+7x^2+12x-11