#color(blue)("y intercept")#
#color(purple)(y_("intercept") " is when "x=0 => y_("intercept")=0)#
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("x intercept")#
#x_("intercept")" at "y=0 = x^2-4x#
Factor out #x# giving:
#color(purple)(y=0=x(x-4) =>x_("intercept")=0 and x_("intercept")=4)#
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("vertex")#
# x_("vertex")# is #1/2# way between x intercepts (mean value)
# color(purple)(x_("vertex") = (0+4)/2=2)#
To determine #y_("vertex")# substitute for #x#
# color(purple)(y_("vertex")=x^2-4x =(2)^2-4(2)=-4)#
# color(purple)("Vertex "->(x,y)=(2,-4)#