Solve D=b^2-4ac

$$D = b ^ { 2 } - 4 a c$$

Solve for a

$$\left\{\begin{matrix}a=\frac{b^{2}-D}{4c}\text{, }&c\neq 0\\a\in \mathrm{R}\text{, }&D=b^{2}\text{ and }c=0\end{matrix}\right.$$

Steps for Solving Linear Equation

Swap sides so that all variable terms are on the left hand side.

$$b^{2}-4ac=D$$

Subtract b^{2} from both sides.

$$-4ac=D-b^{2}$$

The equation is in standard form.

$$\left(-4c\right)a=D-b^{2}$$

Divide both sides by -4c.

$$\frac{\left(-4c\right)a}{-4c}=\frac{D-b^{2}}{-4c}$$

Dividing by -4c undoes the multiplication by -4c.

$$a=\frac{D-b^{2}}{-4c}$$

Divide -b^{2}+D by -4c.

$$a=-\frac{D-b^{2}}{4c}$$

Solve for D

$$D=b^{2}-4ac$$