两题因式分解：35a^4b^3/21a^2b^4d x^2-(y-z)^2/(x+y)^2-z^2 解方程：x+2/5x-3=x+2/6+3x

35a^4b^3/21a^2b^4d
=35/21d*a^(4-2)b^(3-4)
=5a²/(3bd)
x^2-(y-z)^2/(x+y)^2-z^2
=(x+y-z)(x-y+z)/ [(x+y+z)(x+y-z)]
=(x-y+z)/ (x+y+z)
解方程：
(x+2)/(5x-3)=(x+2)/(6+3x)
∵分母6+3x≠0
3(x+2)≠0
∴x+2≠0
于是
5x-3=6+3x
5x-3x=6+3
2x=9
x=9/2