化简求值2根号a-【a-根号a】分之a+根号a【a等于2】

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原式=2√a - (a +√a)/(a-√a)
=2√a - √a(√a +1)/[ √a (√a -1) ]
=2√a - (√a +1)/(√a -1) 分母有理化
=2√a - (√a +1)²/[ (√a +1)(√a -1) ]
=2√a - (a+2√a +1)/(a-1) 通分
=2√a (a-1)/(a-1) -(a+2√a +1)/(a-1)
=(2a√a-2√a)/(a-1) - (a+2√a +1)/(a-1)
=(2a√a-2√a-a-2√a -1)/(a-1)
=(2a√a-4√a-a-1)/(a-1)
当a=2时原式=(2×2√2-4√2-2-1)/(2-1)
=4√2-4√2-3
=-3