Question

已知X（X＋1）－（X的平方＋Y）＝3,求（X的平方＋Y的平方）除以二—XY

Answer 1

X²+X-X²-Y=3

X-Y=3

(X²+Y²)/2-XY

=(X²-2XY+Y²)/2

=(X-Y)²/2

=3²/2

=9/2