Question

已知x=5+2根号6,y=5-2根号6,求下列各式的值

Answer 1

1, ,2x²+4xy+2y²=2（x²+2xy+y²）=2（x+y）².由题意x+y=10,所以原式=200..

2,根（x²-80xy+y²）=根【（x-y）²-78xy】.因为x-y=4根6,.xy=1..所以原式=根18=3根2..