1.-x+4y=9(1)x+3y=5(2)2.2x-3y＝4（1）5x-3y＝19（2）要加减法的，加减法

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 (x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 9y=3x-(x-1),4(x+y)-(2x+4)=8y 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 计算：1.y/4x²-1/12y²+1/6xy 2.3/x-6/1-x-x+5/x²-x3.x/x-y×y²/x+y-x四次方y/x四次方-y四次方÷x²/x²+y²解方程：1.x-1/（x-2）+1=1/2-x2.x+1/x-1-4/x²-1=13.1/x+3-2/3-x=1/x²-9 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) {5(x-3y)-6=2x+1 3(x+6y)+4=9y+19 ｛3分之2（x-y）=4分之x+y-1 6）x+y)=4(2x-y)+16 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 {x+y=1 ,xy=-6{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 帮忙解一些方程组(1)3x-2y=6 2x+3y=17 (2)5x+6y=15.2 3x-2y=-0.4(3)2(x+y)-3y=7 4(x-9)=3(y-2)(4)3(x+y)-4(x-y)=4 x+y/2+x-y/6=1 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 3x-2y=1 4x-5y 初二上学期方程题 4x+y=5 5x+4y=63x-2y=1 2x+3y=13x-2y=7 7x+5y=32x+3y=17 2x-y=-4x+5y=6 2x+y=23x-6y=4 3x+2y=52x+y=73x-4y=53x+y=1x-2y=-1x+y=42x+3y=92x-3y=74x+5y=3x+y=20004x+6y=90003x+5y=113x-2y=42x+3y=215x-2y=5x+y=54x+3y=182x+3y=16x+4y=132x+3y=40x