问题
解答题
计算: (1)-2mn-(3m-1) (2)-32-(
(3)2(x+2)(x-1)-(x-1)2 (4)
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答案
(1)原式=-6m2n+2mn;
(2)原式=-9-3+1
=-11;
(3)原式=2(x2+x-2)-(x2-2x+1)
=x2+4x-5;
(4)8x+5y=-9…① 4x+3y=-7…②
②×2-①得:y=-5,
把y=-5代入①得:8x-25=-9,
解得:x=2
则方程组的解是:
.x=2 y=-5