Question

已知x-y=3,xy=10,xﾁ0ﾅ5+yﾁ0ﾅ5及(x+y)&

Answer 1

x²+y²

=(x²-2xy+y²)+2xy

=(x-y)²+2xy

=3²+2×10

=29

(x+y)²

=x²+2xy+y²

=(x²-2xy+y²)+4xy

=(x-y)²+4xy

=3²+4×10

=49