Question

先化简 后求值：已知（a+2)2+|b-1/4|=0,求5a2b-[2a2b-(ab2-2a2b)-4]-2ab2的值

Answer 1

解析：
已知（a+2)²+|b-1/4|=0，那么有：
a+2=0，b- 1/4=0
解得：a=-2，b=1/4
而5a²b-[2a²b-(ab²-2a²b)-4]-2ab²
=5a²b-(2a²b- ab²+2a²b+4)-2ab²
=5a²b-4a²b+ ab²+4-2ab²
=-a²b+ ab²+ 4
=-ab(a-b)+4
=-(-2)×(1/4)×(-2 - 1/4) +4
=(1/2)×(-9/4) +4
=-9/8+ 4
=2又7/8

Answer 2

（a+2)2+|b-1/4|=0
a+2=0
a=-2

b-1/4=0
b=1/4

5a2b-[2a2b-(ab2-2a2b)-4]-2ab2
=5a2b-2a2b+ab2-2a2b+4-2ab2
=a2b-ab2+4
=ab(a-b)+4
=-2x1/4x(-2-1/4)+4
=9/8+4
=5.125

Answer 3

a=-2,b=1/4
化简结果：ab(a-b)+4
再代入求值就行了

Answer 4

4154699996