4(5x-3)²-9(x-5)²=0
[2(5x-3)+3(x-5)][2(5x-3)-3(x-5)]=0
[10x-6+3x-15][10x-6-3x+15]=0
[13x-21][7x+9]=0
解得x=21/13、和x= - 9/7