1.[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)
2.2/(x-2)+mx/(x^2-4)=3/(x-2)
mx/(x^2-4)=1/(x-2)
mx=(x^2-4)/(x-2)
mx=x+2
(m-1)x=2
m=1时,方程会产生增根
3.(2x+3)/[x*(x-1)*(x+2)]=A/x+B/(x-1)+C/(x+2)
2x+3=A(x-1)*(x+2)+Bx*(x+2)+Cx*(x-1)
2x+3=A(x^2+x-2)+B(x^2+2x)+C(x^2-x)
2x+3=(A+B+C)x^2+(A+2B-C)x-2A
A+B+C=0
A+2B-C=2
-2A=3
A=-3/2,B=5/3,C=-1/6
4.a^2-ab-2b^2=0
(a-2b)(a+b)=0
a=2b或a=-b
a=2b
a/b-b/a-(a^2+b^2)/ab
=2-1/2-(4b^2+b^2)/2b^2
=3/2-5/2
=-1
a=-b
a/b-b/a-(a^2+b^2)/ab
=-1+1-2b^2/(-b^2)
=0+2
=2