Question

数与式 .1、x=根号3 +1,y=根号3 -1,求(x²-2xy+y²)/（x²-y²）的值2、1/a+1/b=根号5

Answer 1

原式=(x-y)² /（x-y)(x+y)=(x-y)/（x+y)=2/2根号3 =根号3/3

原式=a²/b²

1/a+1/b=5^1/2 (a+b)/ab=5^1/2 则易得a+b=5^1/2 ×k ab=1k 解之得b=5^1/2+或-1/2

a=2/5^1/2+或-1

即原式易得=3+或-根号5/2

原式=（x²/(x-1)x-1/x（x-1))(1/(x+1))

=(x+1)(x-1)/x(x+1)(x-1)

=1/x

=根号2/2