问题 解答题
(1)
1
2
xy2-(-4x3y)

(2)a2-a4+(-a23
(3)(x-3y)(x-
1
2
y)

(4)(x+1)(x-1)-(x+2)2
答案

(1)原式=-2x4y3

(2)原式=a6-a6=0;

(3)原式=x2-

1
2
xy-3xy+
3
2
y2=x2-
7
2
xy+
3
2
y2

(4)原式=x2-1-(x2+4x+4)=x2-1-x2-4x-4=-4x-5.

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