Question

已知方程组x+y=4-2k x-3y=2 k是整数

Answer 1

1 x=2y,x+y=4-2k,x-3y=2,so that x=-4,y=- 2,k=5

2 let t1,t2 be in R,such that t1(x+y)+t2(x-3y)=x-y,so t1=t2=1/2,then x-y=1/2(x+y)+1/2(x-3y)=2-k+1=3-k>0,so k2x+6,x