{3x+5y=12,3x—15y=—6这个怎么做

3x—y=5 ,5x+2y=12 ,x=?y=? 若x+y分之x-y=3,求式子x+y分之5(x-y)—2(x-y)分之x+y的值 若x-y分之x+y=3,求式子x+y分之5(x-y)—2（x-y）分之x+y的值 （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 已知X,Y满足x平方+y平方—4x+6y+13=0,求代数式（3x+y）的平方-3（3x-y)(x+y)-(x-3y)(x+3y) 3(x+y)—4(x—y)=4 { (x+y)/2+(x—y)/6=1 2(x-y)/3—x+y/4=1 6(x+y)—4(2x-y)=16 3(x+y)—4(x-y)=4,(x+y/2)+(x-y/6)=1.解方程组 填空题 x+y/4=x-y/6=3x+12y+5/8 x= y= 解方程组：x+y/2+x-y/3=6 4(x+y)-5(x-y)=12 2(x-2y)²-7(x-2y)³+3(2y-x)²+(2y-x)³合并同类项 这个式子2（x-2y)²-7（x-2y)³+3(2y-x)²-(2y-x)³=2（x-2y)²-7（x-2y)³+3(x-2y)²+(x-2y)³=5(x-2y)²-6(x-2y)³=(x-2y)²(5-6x+12y) 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 肖元——解二元一次方程3x+2y=8,6x-5y=-2x+y/2+x-y/3=1.(x+y)-5(x-y)=23x 比如什么代入啊什么的。 先化简,再求值.其中x=-2,y=二分之一 {(x+y)2—(x+y)(x+3Y)—5Y平方}除2y 1) X-Y=1 Y=3/4X+12) Y=4X Y=-3X3) 3X+Y=6 2X+Y=3/24) X+4Y=-1/2 -2X-3Y=15) X-Y=-3/2 -2X+5Y=-4.5