问题 解答题
计算:
(1)(2a-3b)(2a+3b)(-4a2-9b2
(2)(x-2y+3)(x+2y-3)
(3)化简求值:
x2-2x
x2-1
÷(x-1-
2x-1
x+1
)
,(其中x=2)
答案

(1)原式=(4a2-9b2)(-4a2-9b2

=81b4-16a4

(2)原式=x2-4y2+12y-9;

(3)原式=

x(x-2)
(x+1)(x-1)
÷
x2-1-2x+1
x+1

=

x(x-2)
(x+1)(x-1)
×
x+1
x(x-2)

=

1
x-1

当x=2时,原式=

1
2-1
=1.

单项选择题
单项选择题