Question 373451
Range means all possible values of y or f(x).  Here we have a parabola, concave down...its vertex will be a maximum value...
For {{{y = -20x^2 + 10x + 6}}},
the value where x = -b/2a gives you the x coordinate of the max value...here that is
x = -10/-40 = 1/4
Plugging this into the equation, we get
-20(1/4)^2 + 10(1/4) + 6 =
-20/16 + 2.5 + 6 =
-1.25 + 8.5 =
7.25