5x^2-8(3-x)^2-72=0 ==》 5x^2-8(9+x^2-6x)-72=0 ==》-3x^2+48x-144=0 ==》3x^2-48x+144=0 ==》(3x-12)(x-12)=0 ==》x=12或x=4
2x^2+3x+1=0 ==》 （√2x+（3/4)*√2)^2=(3√2-4)/4 ==》√2x+(3/4)*√2=√（（3√2-4)/4） ==》√2x+(3/4) √2=√（3√2-4)/2 ==》x=-√2
2x^2-3x-1=0 ==》△=9+8=17>0 ==》x=(3±√17）/4
（x+1)(x+8)=12 ==》x^2+9x-4=0 ==》△=81+8>0 ==》x=(9±√89)/4
(1-3y)^2+2(3y-1)=0 ==》 9y^2+6x-7=0 ==》△=36+4*7*9>0 ==》y=(6±√288)/18