What is the vertex form of #y=-9x^2 +12x - 18 #? Algebra Quadratic Equations and Functions Vertex Form of a Quadratic Equation 1 Answer Noah G · Suryin =) Dec 26, 2015 Below is the proof (a completion of square) Explanation: #y = -9x^2 + 12x - 18# #y = -9(x^2 - 12/9x) - 18# #y = -9(x^2 - 12/9x + #_ - _ ) - 18# #_ = ((-12/9) / 2)^2# #_ = 4/9# #y = -9(x^2 - 12/9x + 4/9) - 4/9(-9) - 18# #y= -9(x - 2/3)^2 - 14# So, #y = -9x^2 + 12x - 18# is equal to #y = -9(x - 2/3)^2 - 14# Hopefully that explanation helped! Answer link Related questions What is the Vertex Form of a Quadratic Equation? How do you find the vertex form of a quadratic equation? How do you graph quadratic equations written in vertex form? How do you write #y+1=-2x^2-x# in the vertex form? How do you write the quadratic equation given #a=-2# and the vertex #(-5, 0)#? What is the quadratic equation containing (5, 2) and vertex (1, –2)? How do you find the vertex, x-intercept, y-intercept, and graph the equation #y=-4x^2+20x-24#? How do you write #y=9x^2+3x-10# in vertex form? What is the vertex of #y=-1/2(x-4)^2-7#? What is the vertex form of #y=x^2-6x+6#? See all questions in Vertex Form of a Quadratic Equation Impact of this question 474 views around the world You can reuse this answer Creative Commons License