im having trouble working out c in this formula
The method of completing the square can be used to write the expression:
5x^2+20x-12 in the form a(x+b)^2+c where a, b and c are constants. What is the value of c?
In general, for $\displaystyle A,B,C\in\mathbb{R}$ with $\displaystyle A\neq0$, we have
$\displaystyle Ax^{2}+Bx+C=A\Bigg(x^{2}+\frac{B}{A}x\Bigg)+C$
...................._$\displaystyle =A\Bigg(x^{2}+\frac{B}{A}x+\bigg(\frac{B}{2A}\bigg )^{2}-\bigg(\frac{B}{2A}\bigg)^{2}\Bigg)+C$
...................._$\displaystyle =A\Bigg(x^{2}+\frac{B}{A}x+\bigg(\frac{B}{2A}\bigg )^{2}\Bigg)+C-\frac{1}{A}\bigg(\frac{B}{2}\bigg)^{2}$
...................._$\displaystyle =A\Bigg(x+\frac{B}{2A}\Bigg)^{2}+C-\frac{1}{A}\bigg(\frac{B}{2}\bigg)^{2}$