已知实数a满足a的平方+2a-15=0,求.

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已知实数a满足a的平方+2a-15=0,求.

已知实数a满足a的平方+2a-15=0,求.
已知实数a满足a的平方+2a-15=0,求.

已知实数a满足a的平方+2a-15=0,求.
a²+2a-15=0
a²+2a+1=16
(a+1)²=16
原式=1/(a+1) -(a+2)/(a+1)(a-1) ×(a-1)²/(a+1)(a+2)
=1/(a+1)-(a-1)/(a+1)²
=(a+1-a+1)/(a+1)²
=2/(a+1)²
=2/16
=1/8


a²+2a-15=0
a²+2a=15
原式
=1/(a+1)-(a+2)/(a-1)(a+1)×(a-1)²/(a+1)(a+2)
=1/(a+1)-(a-1)/(a+1)²
=(a+1)/(a+1)²-(a-1)/(a+1)²
=(a+1-a+1)/(a+1)²
=2/(a²+2a+1)
=2/(15+1)
=1/8