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

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 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=? 3x+4y=6 2x+3y=5 这题怎么解 X-[8-2(X*Y)]/(Y-20)=X-60和X*Y X*(Y-20)=8是一个题怎么解 由X/Y=2Y/X-Y 怎么解得x=2y? 3x+2=y 5x+4=y 7x+6=y 9x+8=y 11x=y怎么解 4（x+y)^2+25-20(x+y)怎么解, 2x=y 3y=x怎么解 (x/y)2-(x/y)=1怎么解? x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 y'=x+2y+1/2x+4y-1这个微分方程怎么解啊? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x^2-4xy+3y^2=（x-3y)(x-y)x^2-4xy+3y^2 怎么分解成（x-3y)(x-y) [4x-2*(10-x)]-[5y-3*(10-y)]=20这个方程怎么解? 4x+6y+2(6-(x+y))=15这道方程怎么解 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)