1.4X+1.4Y=490 0.7*1.4X+0.9*1.4Y=399

1.4X+1.4Y=490 0.7*1.4X+0.9*1.4Y=399 1.4Y=X 5X+6Y=39 数学一元二次方程组1.4/x+y+6/x-y=39/x-y-1/x+y=1用换元法求 1.4（x-y-1）=3(1-y)-22/x+3/y=22.5(x+y)-6=43x+3y+7y=10 1:4(x-100)+3y=5 2:6(x-y)-2(x+y )=14 x-100=-y 3(x-y)+(x+y)=5 先无视上面的1.4(x-100)+3y=5x-100=-y2.6(x-y)-2(x+y )=143(x-y)+(x+y)=5 x:y=三分之二:二分之一,y:z=0.8:1.4,x:y:z= 用代入法解下列方程组 1.3x+y=4 2.2x-y=1还有 二.1.x+3y=-1 2.3x-2y=8解下列方程组：一.1.x-2y=-1 2.x-y=2-2y二.1.4（x-y-1）=3（1-y-2）2.二分之x=三分之y=2 x+y=1. 先化简 再求值(x-2y)(2y-x)+(2x+y)(2x-y )-(x-2y)(2x+y) 其中x=-2,y=-1. x^2-y分之y(x-y)-x(x+y)除以x+y分之x^2+y^2.其中x=2,y=-1.先化简再求值. 方程题4道1.4(x-y-1)=3(1-y)+3.5 (x/2)+(y/3)=2 2.2(x-y)/3-(x+y)/4=13/6 6(x+y)-4(2x-y)=16 3.3x-y+z=3 2x+y-3z=9 x+y+z=12 4.5x-4y+4z=13 2x+7y-3z=19 3x+2y-z=18 解下列方程组 1.4x+3y=24 5x-y=30 2.5x+3y=8 7x-3y+42.5x+3y=8 7x-3y=4 {x/2=y/5 {25%x+40%y=1.4{x/2=y/5{25%x+40%y=1.4 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = 1.4x^2 - 4xy + y^2 - 44x + 22y + 402.( 1 - x^2 )( 1 - y^2 ) + 4xy3.x^2 + x + 1 =0 x-y=-2 x+y=1.x和y分别等于多少?x-y=-2x+y=1.x和y分别等于多少? y=x,y=-x,y=x+1,y=x-1,y=-x+1,y=-x-1.判断各直线经过哪个象限