5X+4Y=20 4X+5Y=16 怎么解?求问这题怎么做

5x-4y(y-x)=? 5x+4y=22 4x+y=3y+x 怎么解 二元一次方程(x+y)/2+(x-y)/3=6,4(x+y)-5(x-y)=2怎么算 x+y／y=5／4,则x／y=---------------- 已知：4x = 5y,求(x+y) ：y （5x+3y)(3y-5x)-(4x-y)(4y+x)= 3x+2=y 5x+4=y 7x+6=y 9x+8=y 11x=y怎么解 x*x+2x+y*y-4y+5=0 x= y= 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 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 这题怎么解?X-Y=4,2X+Y=20,X=?Y=?3X+2Y=14,2X-3Y=5,X=?Y=?写出具体算式 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 y=|-x.x+4x+5| 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=? 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? X^4-5X^2+4Y^4怎么变化成(X+Y)(X-Y)(X+2Y)(X-2Y)这步?就算是把(X+Y)(X-Y)(X+2Y)(X-2Y)算出来 也是=（X^2-Y^2)(X^2-4Y^2)=X^4-5X^2Y^2+4Y^4...也不是=(X^4-5X^2+4Y^4)