x² -10x +24=0
（x-6)(x-4)=0
x-6=0 x=6
x-4=0 x=4
2）2y²+y-6=0
(2y-3)(y+2)=0
2y-3=0 y=3/2
y+2=0 y=-2
（3）5x²+11x+6=0
(5x+6)(x+1)=0
5x+6=0 x=-6/5
x+1=0 x=-1
（4）6x²+7x+2=0
(3x+1)(x+2)=0
3x+1=0 x=-1/3
x+2=0 x=-2
（5）6x²+x-15=0
(3x+5)(2x-3)=0
3x+5=0 x=-5/3
2x-3=0 x=3/2
（6）6x²-31x+35=0
(3x-5)(2x-7)=0
3x-5=0 x=5/3
2x-7=0 x=7/2
（7）6x² -13x-15=0
(6x+5)(x-3)=0
6x+5=0 x=-5/6
x-3=0 x=3
（8）2x²+3x+1=0
(2x+1)(x+1)=0
2x+1=0 x=-1/2
x+1=0 x=-1