如何得出(x²+3xy+2y²)=(x+2y)(x+y)的?

已知x+y=4.x-y=6.求代数式xy(y²+y)-y²(xy+2x)-3xy的值 已知x/y=3,求x²+2xy-3y²/x²-xy+y²的值 已知y/X=3,求x²-xy+y²/x²+2xy-3y²的值 已知x/y=2,求x²-xy+3y²/x²+xy+6y²的值 1/x+1/y=5,求2x-3xy+2y/x²+xy+y的值 已知x-3y=0,求(x²-2xy+y²/x-y)-2y的值 x²-2xy+y²分之x²+2xy-3y³如何因式分解 已知x-3y=0,求2x+y/x²-2xy ×（x-y)的值 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 急![(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y)]÷(2xy) 若正数x,y满足x²-y²=2xy,求（x-y)/(x+y)的值 正数x,y满足x²-y²=2xy,求x-y/x+y的值