问题 解答题
计算:
(1)x2y-
2
5
x2y-2x2y

(2)(3a-2)-3(a+5)
(3)(4a2b-5ab2)-(3a2b-4ab2
(4)3x2-[7x-3(4x-3)-2x2].
答案

(1)原式=(1-

2
5
-2)x2y

=-

7
5
x2y;

(2)原式=3a-2-3a-15

=-17;

(3)原式=4a2b-5ab2-3a2b+4ab2

=a2b-ab2

(4)原式=3x2-[7x-12x+9-2x2]

=3x2-7x+12x-9+2x2

=5x2+5x-9.

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