解答题:(1)x(y-1)-y(x-1)(2)(x-3y)(x+3y)-(x-3y)2(3)12x-2(x-13y2)+(-32x+13y2),其中x=-1,y=12-数学

题目简介

解答题:(1)x(y-1)-y(x-1)(2)(x-3y)(x+3y)-(x-3y)2(3)12x-2(x-13y2)+(-32x+13y2),其中x=-1,y=12-数学

题目详情

解答题:
(1)x(y-1)-y(x-1)
(2)(x-3y)(x+3y)-(x-3y)2
(3)
1
2
x-2(x-
1
3
y2)+(-
3
2
x+
1
3
y2),其中x=-1,y=
1
2
题型:解答题难度:中档来源:不详

答案

(1)原式=xy-x-xy+y=-x+y;
(2)原式=x2-(3y)2-x2+6xy+(3y)2=6xy-18y2;
(3)原式=class="stub"1
2
x-2x+class="stub"2
3
y2-class="stub"3
2
x+class="stub"1
3
y2=-3x+y2,
把x=-1,y=class="stub"1
2
代入上式,得
上式=-3×(-1)+(class="stub"1
2
)
2

=3+class="stub"1
4

=class="stub"13
4

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