Question

Solve : $x^2-8x+15=0$ by completing a square method.

Answer 1

Given equation

$x^2-8x+15=0$

Let $16$ add and subtraction in the given equation.

$x^2-8x+16-16+15=0$

$\left(x^2-8x+16\right)-1=0$

${\left(x-4\right)}^2-1=0$

$\begin{array}{c}{\left(x-4\right)}^2=1\\ x-4=\sqrt{1}\\ x-4=1\\ x=1+4=5\end{array}$]

Therefore,

$x=5,3$