(1)原式=(x+3)(x+9)=0,x=-3或-9
(2)原式=5x^2-x-4=0;(x-1)(5x+4)=0,x=1或-4/5
(3)(3x-4)(x-6)=0,x=4/3或6
(4)3x^2+10x-8=0;(x+4)(3x-2)=0,x=-4或2/3