What can you add to #x^2-9x# to get a perfect square trinomial? Algebra Polynomials and Factoring Factor Polynomials Using Special Products 1 Answer vanessa May 12, 2018 #20.25# Explanation: In a perfect square, the equation is #ax^2+bx+c#, where #abs(b) = 2asqrt(c)#. Therefore, to find #c#, plug in #a# and #b#. #abs(b)=2asqrt(c)# #abs(-9) = 2*1*sqrt(c)# #9 = 2*sqrt(c)# #4.5 = sqrt(c)# #20.25 = c# Answer link Related questions How do you factor special products of polynomials? How do you identify special products when factoring? How do you factor #x^3 -8#? What are the factors of #x^3y^6 – 64#? How do you know if #x^2 + 10x + 25# is a perfect square? How do you write #16x^2 – 48x + 36# as a perfect square trinomial? What is the difference of two squares method of factoring? How do you factor #16x^2-36# using the difference of squares? How do you factor #2x^4y^2-32#? How do you factor #x^2 - 27#? See all questions in Factor Polynomials Using Special Products Impact of this question 4368 views around the world You can reuse this answer Creative Commons License