解(2x+1)的平方=9(x-3)的平方
(2x+1)^2-9(x-3)^2=0
[2x+1+3(x-3)][2x+1-3(x-3)]=0
(5x-8)(-x+10)=0
5x-8=0 -x+10=0
x=8/5 x=10