问题
解答题
(1)分解因式:4a(x-y)-2b(y-x) (2)用简便方法计算:20012-4002+1 (3)已知x2+2x-1=0,求(3x-2)(3x+2)-2x(x-1)-(2x-1)2的值 (4)已知:
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答案
(1)原式=4a(x-y)+2b(x-y)=(4a+2b)(x-y);
(2)原式=20012-2×2001+1=(2001-1)2=20002=4000000;
(3)原式=9x2-4-2x2+2x-4x2+4x-1=3x2+6x-5,
当x2+2x-1=0,即x2+2x=1时,原式=3(x2+2x)-5=3-5=-2;
(4)将
,x=1 y=- 1 2
代入方程得:x=2 y= 1 2
,a-
b=31 2 2a+
b=31 2
解得:a=2,b=-2,
则原式=4-4=0.