Sometimes factorisation of given quadratic equation is not possible coefficients in the quadratic equation are large numbers, then it may be difficult to factorise, 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.

1. Write equation in standard form.
2. Shift constant term on RHS.
3. Make coefficient of as one.
4. Add on both sides
5. 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