What is the the vertex of #y =-2x^2 + 12x + 9 #?
1 Answer
Jun 4, 2018
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)#
