已知A=x³-5x²,B=x²-11x+6,求:⒈A+2B;⒉当x=-1时,求A+5B

问题描述:

已知A=x³-5x²,B=x²-11x+6,求:⒈A+2B;⒉当x=-1时,求A+5B

(1)原式=x3-5x2+2(x2-11x+6)
=x3-3x2-22x+12;
(2)A+5B=x3-5x2+5(x2-11x+6)
=x3-55x+30;
当x=-1时,
原式=-1+55+30=84.