Question

x^2-y^2=6,x-y=2,请求x^2+y^2的值

Answer 1

x-y=2

x=y+2

x^2-y^2=6

(y+2)^2-y^2=6

y^2+4y+4-y^2=6

4y=2

y=1/2

x=y+2=1/2+2=5/2

x^2+y^2

=(5/2)^2+(1/2)^2

=25/4+1/4

=26/4

=13/2