Sometimes factorization of given quadratic equation is not possible coefficients in the quadratic equation are large numbers, then it may be difficult to factorize, so in this case, we can use completing square method.
In order to solve the quadratic equation by completing square method, we have the following steps.

Write equation in standard form.

Shift constant term on RHS.

Make coefficient of as one.

Add on both sides

Finally, simplify the equation to get the required roots.
Example:
Solve the equation by the method of completing square.
Solution:
Write the equation in standard form
Shift constant term on RHS, we get
Make the coefficient of as divide the equation by
Now adding on both sides, we get
Taking square root on both sides, we get
Either or
Example:
Solve the equation by the method of completing square.
Solution:
Write the equation in standard form as
Multiplied by to make coefficient of as positive
Shift constant term on RHS, we get
Now adding on both sides, we get
Taking square root on both sides, we get
Either or