cos4x怎么化简 先化简,后求值(x^2y-4^3^/x^2+4xy+4y^2)·(4xy/x-2y+x)，其中x=根号2-1，y=根号2+1

先化简,后求值(x^2y-4^3^/x^2+4xy+4y^2)·(4xy/x-2y+x)，其中x=根号2-1，y=根号2+1  

先化简,后求值(x^2y-4^3^/x^2+4xy+4y^2)·(4xy/x-2y+x)，其中x=根号2-1，y=根号2+1 实在想起不起了了，速求

(x^2y-4^y3^/x^2+4xy+4y^2)·(4xy/x-2y+x)，其中x=根号2-1，y=根号2+1
=(x²y-4y³)/(x+2y)²*(4xy+x²-2xy)/(x-2y)
=y(x+2y)(x-2y)/(x+2y)²*x(x+2y)/(x-2y)
=xy
=(√2-1)(√2+1)
=2-1
=1

先化简，后求值：(x^2y-4y^3)/(x^2+4xy+4y^3)*((4xy)/(x-2y)+x)其中x=根号2-1y=根号2+1

题是这样的吧(x^2y-4y^3)/(x^2+4xy+4y^2)*((4xy)/(x-2y)+x)，?感觉是4y²
原式=y(x+2y)(x-2y)/(x+2y)² * (4xy +x²-2xy)/(x-2y)
=y(x+2y)(x-2y)/(x+2y)² * x(x+2y)/(x-2y)
=xy
∵x=√2-1 ,y=√2+1
∴xy=1
∴原式=1

(x^2y-4y^2/x^2+4xy+4y^2)(4xy/x-2y+x)其中x=根号2-1y=根号2+1

你题目是不是打错了

先化简，再求值((x-y)/(x-2y))/((x^2-y^2)/(x^2-4xy+2y^2),x=1+根号2,y=1-根号2 这

解：原式=[(x-y)/(x-2y)][(x-2y)^2/(x+y)(x-y)
约分后=(x-2y)/(x+y)把X和Y带进式子得到
原式=2分之1+3倍根号2

（x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2)先化简后求值 其中x=-2，y=3

（x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2)
=（x-y/x+2y)/(x-y)(x+y)/(x+2y)^2
=1/(x+y)/(x+2y)
=(x+2y)/(x+y)
代入
=4

（x-y/x+2y)/(x^2-y^2/x^2+4xy+4y^2),其中x=1-根号2 y=根号2-2

先对式子化简 对分母x^2-y^2/x^2+4xy+4y^2=（x+2y）^2-y^2/x^2=(x+2y-y/x)(x+2y+y/x)
原式=（x-y/x+2y)/(x+2y-y/x)(x+2y+y/x)=1/(x+2y+y/x)，再待数字计算

先化简在求值 当x=9,y=4时,求代数式根号x^3+x^2y+1/4xy^2+根号1/4x^2y+xy^2+y^3的值，

根号(x^3+x^2y+1/4xy^2)+根号(1/4x^2y+xy^2+y^3)
=√x(x²+xy+y²/4)+√y(x²/4+xy+y²)
=√x(x+y/2)²+√y(x/2+y)²
=(x+y/2)√x+(x/2+y)√y
代入x=9 y=4
原式=(9+2)√9+(9/2+4)√4
=11*3+(17/2)*2
=33+17
=50
希望能帮到你，祝学习进步O(∩_∩)O

先化简，再求值：X-Y/X-2Y除以X^2-Y^2/X^2-4XY+4Y^2.其中X=1加根号2,Y=1减根号2。急！求详细步骤！

X-YX-2Y除以X^2-Y^2X^2-4XY+4Y^2
=X-YX-2Y乘(X-2)^2(X+Y)(X-Y)
=X-2YX+Y
把X=1+根号2,Y=1-根号2,代入式子中
=(1+根号2)-2(1-根号2)(1+根号2)(1-根号2)
=3倍根号2-12

先化简再求值:4xy-[(x^2+5xy-y^2)-(x^2+3xy-2y^2)]其中x=1/4,y=1/2

4xy-[(x^2+5xy-y^2)-(x^2+3xy-2y^2)]
=4xy-(x^2+5xy-y^2)+(x^2+3xy-2y^2)
=4xy-x^2-5xy+y^2+x^2+3xy-2y^2
=2xy-y^2
当x=1/4，y=1/2时
原式=1/4-1/4
=0