问题
解答题
| 计算： ①
②
③
④
|
答案
①
÷（-y 7x
）=2 x
×（-y 7x
）=-x 2
；y 14
②原式=
=a-2-(2a-3) a-1
=a-2-2a+3 a-1
=-a+1 a-1
=-1；-(a-1) a-1
③原式=
-12 (m-3)(m+3)
=2(m+3) (m-3)(m+3)
=12-(2m+6) (m-3)(m+3)
=-2m+6 (m-3)(m+3)
=--2(m-3) (m-3)(m+3)
；2 m+3
④原式=
-x2 x-1
=(x-1)2 x-1
=x2-(x2-2x+1) x-1
=x2-x2+2x-1 x-1
．2x-1 x-1