Given the equation;
[tex]y=5x^2+20x-1[/tex]
so, by completing the square the equation will be:
[tex]\begin{gathered} y=5(x^2+4x)-1 \\ y=5(x^2+4x+4)-1-20 \\ y=5(x+2)^2-21 \\ \\ y=5(x-(-2))^2-21 \end{gathered}[/tex]
So, the vertex of the equation will be at ( -2 , -21 )
So, the equation of the axis of symmetry is:
[tex]x=-2[/tex]
