Question 463928
By "looking" at:
y = 0.005x^2 -2x +200 
we know that it is a parabola that opens upwards (because of the positive coefficient associated with the x^2 term).
So, the vertex would be the lowest point and where it would turn upwards:
x = -b/(2a)
x = -(-2)/(2*0.005)
x = 2/0.010
x = 200 (this is what they're looking for)