Question

先化简再求值[1/（x²+4x+4）+1/x²+2x]÷（x+1）/(x+2)，其中x=3

先化简再求值
[1/（x²+4x+4）+1/x²+2x]÷（x+1）/(x+2)
其中x=3
今天圣诞节，也祝各位圣诞快乐

Answer 1

[1/(x²+4x+4)+1/(x²+2x)]÷(x+1)/(x+2)
=[1/(x+2)²+1/x(x+2)]÷(x+1)/(x+2)
=[1/(x+2)+1/x]÷(x+1)
=[(x+x+2)/x(x+2)]÷(x+1)
=2(x+1)/x(x+2)÷(x+1)
=2/x(x+2)
=2/[3*(3+2)]
=2/15

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