化简：(1)x^2-4y^2/x-2y(2)a^3-2a/a(3)x^2-x/x-1(4)(x+2)^2-(x-2)^2/x化简：(1)x^2-4y^2/x-2y(2)a^3-2a/a(3)x^2-x/x-1(4)(x+2)^2-(x-2)^2/x(5)x^2-2xy+y^2-1/x-y-1(6)已知x/2=y/3=z/4,则xy+yz+zx/x^2+y^2+z^2=问你几道题,可以马上回答我吗

Question

化简：(1)x^2-4y^2/x-2y (2)a^3-2a/a (3)x^2-x/x-1 (4)(x+2)^2-(x-2)^2/x
化简：(1)x^2-4y^2/x-2y
(2)a^3-2a/a (3)x^2-x/x-1
(4)(x+2)^2-(x-2)^2/x
(5)x^2-2xy+y^2-1/x-y-1
(6)已知x/2=y/3=z/4,则xy+yz+zx/x^2+y^2+z^2=
问你几道题,可以马上回答我吗?

Answer 1

(1)x^2-4y^2/x-2y =(x+2y)(x-2y)/(x-2y)=x+2y
(2)a^3-2a/a=a(a^2-2)/a=a^2-2
(3)x^2-x/x-1 =x(x-1)/(x-1)=x
(4)(x+2)^2-(x-2)^2/x=[(x+2)+(x-2)]*[(x+2)-(x-2)]/x=2x*4/x=8
(5)x^2-2xy+y^2-1/x-y-1=[(x-y)^2-1]/(x-y-1)=(x-y+1)(x-y-1)/(x-y-1)=x-y+1
(6)z=2x,y=3/2x
xy+yz+zx/x^2+y^2+z^2
=[x*(3/2x)+(3/2x)*2x+2x*x]/[x^2+(3/2x)^2+(2x)^2
=(3/2x^2+3x^2+4x^2)/(x^2+9/4x^2+4x^2)
=17/2x^2/(29/4x^2)
=34/29