$\begin{array} { l }a=4,& b=0,& c=-225\end{array}$
Substitute $a=4$, $b=0$ and $c=-225$ into the quadratic formula $x=\frac{ -b\pm\sqrt{ {b}^{2}-4ac } }{ 2a }$$x=\frac{ -0\pm\sqrt{ {0}^{2}-4 \times 4 \times \left( -225 \right) } }{ 2 \times 4 }$
Removing $0$ doesn't change the value, so remove it from the expression$x=\frac{ \sqrt{ {0}^{2}-4 \times 4 \times \left( -225 \right) } }{ 2 \times 4 }$
$0$ raised to any positive power equals $0$$x=\frac{ \sqrt{ 0-4 \times 4 \times \left( -225 \right) } }{ 2 \times 4 }$
Calculate the product$x=\frac{ \sqrt{ 0+3600 } }{ 2 \times 4 }$
Multiply the numbers$x=\frac{ \sqrt{ 0+3600 } }{ 8 }$
Removing $0$ doesn't change the value, so remove it from the expression$x=\frac{ \sqrt{ 3600 } }{ 8 }$
Evaluate the square root$x=\frac{ 60 }{ 8 }$
Write the solutions, one with a $+$ sign and one with a $-$ sign$\begin{array} { l }x=\frac{ 60 }{ 8 },\\x=\frac{ -60 }{ 8 }\end{array}$
Cancel out the common factor $4$$\begin{array} { l }x=\frac{ 15 }{ 2 },\\x=\frac{ -60 }{ 8 }\end{array}$
Simplify the expression$\begin{array} { l }x=\frac{ 15 }{ 2 },\\x=-\frac{ 15 }{ 2 }\end{array}$
The equation has $2$ solutions$\begin{align*}&\begin{array} { l }x_1=-\frac{ 15 }{ 2 },& x_2=\frac{ 15 }{ 2 }\end{array} \\&\begin{array} { l }x_1=-7.5,& x_2=7.5\end{array}\end{align*}$