$\begin{array} { l }a=-4,& b=6,& c=0\end{array}$
Substitute $a=-4$, $b=6$ and $c=0$ into the quadratic formula $y=\frac{ -b\pm\sqrt{ {b}^{2}-4ac } }{ 2a }$$y=\frac{ -6\pm\sqrt{ {6}^{2}-4 \times \left( -4 \right) \times 0 } }{ 2 \times \left( -4 \right) }$
Any expression multiplied by $0$ equals $0$$y=\frac{ -6\pm\sqrt{ {6}^{2}-0 } }{ 2 \times \left( -4 \right) }$
Multiply the numbers$y=\frac{ -6\pm\sqrt{ {6}^{2}-0 } }{ -8 }$
Removing $0$ doesn't change the value, so remove it from the expression$y=\frac{ -6\pm\sqrt{ {6}^{2} } }{ -8 }$
Reduce the index of the radical and exponent with $2$$y=\frac{ -6\pm6 }{ -8 }$
Use $\frac{ -a }{ b }=\frac{ a }{ -b }=-\frac{ a }{ b }$ to rewrite the fraction$y=-\frac{ -6\pm6 }{ 8 }$
Write the solutions, one with a $+$ sign and one with a $-$ sign$\begin{array} { l }y=-\frac{ -6+6 }{ 8 },\\y=-\frac{ -6-6 }{ 8 }\end{array}$
Simplify the expression$\begin{array} { l }y=0,\\y=-\frac{ -6-6 }{ 8 }\end{array}$
Simplify the expression$\begin{array} { l }y=0,\\y=\frac{ 3 }{ 2 }\end{array}$
The equation has $2$ solutions$\begin{align*}&\begin{array} { l }y_1=0,& y_2=\frac{ 3 }{ 2 }\end{array} \\&\begin{array} { l }y_1=0,& y_2=1.5\end{array}\end{align*}$