5x²－7x-6＝0
(5x+3)*(x-2)=0
x=2 或5x+3=0
x=-3/5
4x²-7x-3＝0
⊿=b²－4ac=97
x=(-b-√ ⊿)/2a=(7-√ 97)/10
或x=(-b+√ ⊿)/2a=(7+√ 97)/10