3(X-1)+5(4Y+2)=7 4(X+5)-3(Y+1)=12 我一点也不懂这题

若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 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 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 3x-y+x=3 4【X-y-1】=3【1-y】-1 5x-4y+4x=3 2x+y-3x=11 【 x除以2 】-【y 除以3】 =2 2x+7y-3x=19 x+y+x=12 3x+2y-x=18 -(5x+y)-7(x-y) -2分之1（x+y）+4分之1（x+2y） 4x-2（x-2） -2x-（3x-1） x-(5x-2y)+2(2x-y) (3x+2y)(4x-5y)-12(x+y)(x-y)+7xy,其中x=2011,y=-1, 证明：代数式[(x+y)(x-y)-(x+y)^2-2y(x-y)-2xy]/xy 的值为x,y的值无关 解方程 (x+1)^5/(-1-x)^4=3x+7一定要100%正确阿. {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 解下列方程组或不等式组...一{ x(x-5)+y(y+6)=x平方+y平方-39 二 { x(x+7)-y(y-8）=x平方-y平方-11一{x（2x-5）大于2x平方-3x-4二{（x+1）（x-3）+8x大于（x+5）（x-5）-2 例X=1 y=21.X+Y=5 X-Y=15 2.2X+3Y=4 5X+6Y=7 3.X+3Y=5 3X+Y=-1 4.2X+Y=3 3X+5Y=11 5.4X+3Y=6 2X+Y=4 6.X+Y=180 X=3Y-10 7.3X-2Y=3 2X-Y=7 8.5X+3Y=7Y X+Y=45 9.3X+4Y=126X+8Y=24 X:6Y=1:4 10.X+Y=138 X-45=Y+53 11.X+Y=60 14Y=20X 12.2X+3Y=15.5 5X+6Y=35 13.X+Y=170 3 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²= {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 (2/2)1-2x),2y-[y-3(y-1)]=5,3x-2(3x+1)+7x=6x-4(4-3x), 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5