y=2x^2+5x-2
2x^2+5x-2=0
ax^2+bx+c=0
a=2, b=5, c=-2
\Delta=b^2-4ac=5^2-4*2*(-2)=25+16=41
\sqrt\Delta=\sqrt{41}
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{-5-\sqrt{41}}{2*2}=\frac{-5-\sqrt{41}}{4}
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{-5+\sqrt{41}}{2*2}=\frac{\sqrt{41}-5}{4}