若a-b/b=1/2,则3a2-5ab+2b22a2+3ab-5b2的值是_.
问题描述:
若
=a-b b
,则1 2
的值是___.3a2-5ab+2b2
2a2+3ab-5b2
答
3a2-5ab+2b2
2a2+3ab-5b2
=
(3a-2b)(a-b) (2a+5b)(a-b)
=
,3a-2b 2a+5b
∵
=a-b b
,1 2
∴a=
b,3 2
∴原式=
=
b-2b9 2 3b+5b
.5 16
故填空答案:
.5 16