Use the method of completing the square to solve,

 Use the method of completing the square to solve,

x2 + bx+ c = 0

where b and c are real numbers.

 

\(x^2+bx+c=0\\ x^2+bx=-c\\ x^2+bx+(\frac{b}{2})^2=-c+(\frac{b}{2})^2\\ (x+\frac{b}{2})^2=-c+\frac{b^2}{4}\\ (x+\frac{b}{2})^2=\frac{b^2-4c}{4}\\ x+\frac{b}{2}=\pm \sqrt{\frac{b^2-4c}{4}}\\ x+\frac{b}{2}=\frac{\pm\sqrt{b^2-4c}}{2}\\ x=\frac{-b}{2}\pm\frac{\sqrt{b^2-4c}}{2}\\ x=\frac{-b\pm \sqrt{b^2-4c}}{2}\\ \)

 

And there we have the quadratic formula for when a=1