Question

若﹛2010X+2011y=2009,2011X+2010y=2012.求（x+y)²+（x-y)²

Answer 1

2010x+2011y=2009 (1)

2011x+2010y=2012 (2)

(1)+(2)

4021x+4021y=4021

x+y=1

(2)-(1)

x-y=3

(x+y)²+(x-y)²=1²+3²=1+9=10