您好！解：A+2B=2x^2-3x+1+2(-x^2+2x-3) =x-5 A-B=2x^2-3x+1-(-x^2+2x-3) =3x^2-5x+4
A=4XX-3X+1,B=-XX+2X-3,A+2B=4XX-3X+1-2XX+4X-6=XX+X-5 A-B=4XX-3X+1+XX-2X+3=5XX-5X+4
B=?题目有问题
