3x+5y=k+2(1) x+y=k (2)
(2)X3得:3x+3y=3k(3)
(3)-(1)得:(3x+3y)-(3x+5y)=3k-(k+2)
3x+3y-3y-5y=3k-k-2
y=-k+1
把y=-k+1代入(2)得:x-k+1=k
x=2k-1
把{ x=2k-1; y=-k+1代入2
3x+5y=k+2(1) x+y=k (2)
(2)X3得:3x+3y=3k(3)
(3)-(1)得:(3x+3y)-(3x+5y)=3k-(k+2)
3x+3y-3y-5y=3k-k-2
y=-k+1
把y=-k+1代入(2)得:x-k+1=k
x=2k-1
把{ x=2k-1; y=-k+1代入2