First, put the first 2 terms (x^2 and bx) into parentheses. Remember that c goes outside the parentheses. Next, take out a greatest common factor if possible. In the example to the right, a greatest common factor of -9 can be taken out. keep in mind that variables don't count.

 

 

Now divide your value of b by 2 and then square your answer. Whatever the answer you get, add it to the equation, and also subtract it so that the equation is not changed.

 

 

 

 

 

Now take out the negative number that is inside the brackets, by multiplying it by the greatest common factor. Outside of the brackets, you may need to add or subtract some numbers. So do all that needs to be done before moving on. In this case, we need to add 36 and 8 outside the brackets.

 

 

 

 

The last step to do is factoring all that is inside the brackets. It is a perfect square trinomial. To review how perfect square trinomials are factored, review the previous factoring lesson.

 

 

The final answer should be in vertex form. To review how vertex form works, click here.