How to find the value of r ?
A quadratic function #f(x)=-3x^2 +kx +12# , where #k# is a constant, has maximum point #(2,r)# . Find the values of #k# and #r# .
A quadratic function
1 Answer
Aug 30, 2017
Explanation:
#"substitute " (2,r)" into the equation"#
#r=-12+2k+12rArrr=2kto(color(red)(1))#
#"let x = 0 for y-intercept"#
#rArry=12larrcolor(red)" y-intercept"#
#"the equation in "color(blue)"vertex form"# is.
#y=-3(x-2)^2+r#
#"substitute "(0,12)" into the vertex form of the equation"#
#12=-12+rrArrr=24#
#"from "(color(red)(1))#