280=3n²-2n
-3n²+2n+280=0
Δ=b²-4*a*c
Δ=4+4*280*3
Δ=4+3360
Δ=3364
√Δ=√3364=58
[tex]x_1= \frac{-b+\sqrt{\Delta}} {2*a} = \frac{-2+58}{2*(-3)} = \bold{\frac{56}{-6} =-9,(3)}
\\\\
x_2=\frac{-b-\sqrt{\Delta}} {2*a} = \frac{-2-58}{-6} = \frac{-60}{-6}=\bold{10} [/tex]
