若1a−1b=5,则分式2a+3ab−2ba−2ab−b的值为( ) A.135 B.−35 C.35 D.1
问题描述:
若
−1 a
=5,则分式1 b
的值为( )2a+3ab−2b a−2ab−b
A.
13 5
B. −
3 5
C.
3 5
D. 1
答
∵
−1 a
=5,1 b
∴
=5,b−a ab
∴a-b=-5ab,
∴原式=
2(a−b)+3ab (a−b)−2ab
=
2×(−5ab)+3ab −5ab−2ab
=
−7ab −7ab
=1.
故选D.