5√17/5+1/2√20-5/2√1/5+√45 - 知识问答

5√17/5+1/2√20-5/2√1/5+√45-1/2√405

1个回答

5√(17/5)+1/2√20-5/2√(1/5)+√45-1/2√405
=√(25*17/5)+1/2*2√5-1/2√(25*1/5)+3√5-9/2√5
=√85+√5-1/2√5+3√5-9/2√5
=√85+√5+3√5-1/2√5-9/2√5
=√85+4√5-5√5
=√85-√5

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