What is the the vertex of #y =-2x^2 + 12x + 9 #?

1 Answer
Jim G.
Jun 4, 2018

#"vertex "=(3,27)#

Explanation:

#"given a quadratic in "color(blue)"standard form ";ax^2+bx+c#

#"then the x-coordinate of the vertex is "#

#•color(white)(x)x_(color(red)"vertex")=-b/(2a)#

#-2x^2+12x+9" is in standard form"#

#"with "a=-2,b=12" and "c=9#

#x_("vertex")=-12/(-4)=3#

#"substitute this value into the equation for y"#

#y_("vertex")=-2(3)^2+12(3)+9=27#

#color(magenta)"vertex "=(3,27)#

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