数学初一下册二元一次方
1.若方程组2ax+(a-1)y=6,4x-3y=14的值互为相反数,则a的值为多少
2.解方程 {3（x-1）=y+5···①
{5(y-1)=3(x+5)···②
3.{3(x+y)-4(x-y)=4···①
{x+y/2=x-y/6=1···②