Question

已知:x的平方+y的平方=17,xy=-4,且x大于y,(1)求x-y的值;(2)求x+y的值;(3)求x的平方+y的平

Answer 1

1.

(x-y)²

=x²+y²-2xy

=17-2×(-4)

=35

x-y=√35

2.

(x+y)²

=x²+y²+2xy

=17-8

=9

x+y=±3

3.

这个是求x²-y²的值吧?

x²-y²

=(x-y)(x+y)

=±3*√35