Answer:
c = 3
Step-by-step explanation:
The parabola y=-2x^(2)+8x-c has its vertex at (2,5). What is the value of c?
we know the vertex... then the vertex form looks like:
y = a *(x - 2)^2 + 5
expanded out we get :
a (xx - 4x + 4) + 5 = axx - 4ax + 4a + 5
compare that to y=-2x^(2)+8x-c
axx - 4ax + 4a + 5 = -2x^(2)+8x-c
solve...
axx = -2xx, a = -2
then -c = 4a + 5
-c = 4*-2 + 5 = -8 + 5 = -3
c = 3
