(1)已知X={根号3}-1/{根号3}+1,Y={根号3}+1/{根号3}-1,求{根号X平方+Y平方-2}(2)已知X={根号7+根号5}/2,Y={根号7-根号5}/2,求(X立方+Y四次方)乘(X+Y)的值“/”统一为分数线

问题描述:

(1)已知X={根号3}-1/{根号3}+1,Y={根号3}+1/{根号3}-1,求{根号X平方+Y平方-2}
(2)已知X={根号7+根号5}/2,Y={根号7-根号5}/2,求(X立方+Y四次方)乘(X+Y)的值
“/”统一为分数线

1.先简化 分母有理化
x=2-√3 y=2+√3
x*x=7-4√3 y*y=7+4√3
所以x*x+y*y-2=12
所以原式=2√3
2.x+y=√7 xy=1/2
(xxx+yyyy)(x+y)=(x+y)(xxx+yyy)y=(x+y)(x+y)(xx-xy+yy)y
=(x+y)(x+y)[(x+y)(x+y)-3xy]y
=√7*√7[√7*√7-3*1/2](√7-√5)/2
=7*13/2*(√7-√5)/2
=91/4*(√7-√5)