因式分解的简单应用 (23 12:14:38)
问题描述:
因式分解的简单应用 (23 12:14:38)
1. x2-6x=-9
2. (x+2)2=(2x+1)2
3. 9(x+3)2=(2x-5)2
4. 若a2+a-3=0,求a4+2a3-a-1的值
答
1.x2-6x=-9 x^2-6x+9=0(x-3)^2=0x=32.(x+2)2=(2x+1)2 [(x+2)+(2x+1)][(x+2)-(2x+1)]=0(3x+3)(-x+1)=03(x+1)(1-x)=0x1=-1,x2=13.9(x+3)2=(2x-5)2 [3(x+3)+(2x-5)][3(x+3)-(2x-5)]=0(5x+4)(x+14)=0x1=-4/5,x2=-144.若a...