约分:①5ab/20a2b= _ ,②x2-9x2-6x+9= _ .
问题描述:
约分:①
= ___ ,②5ab 20a2b
= ___ .
x2-9
x2-6x+9
答
①
=5ab 20a2b
;1 4a
②
=
x2-9
x2-6x+9
=(x+3)(x-3) (x-3)2
.x+3 x-3