Help on Quadratic Functions

Question

A projectile follows a parabolic path whose height, in meters, is given by the function f(x) = -x²  +2x + 2

  

Find the maximum horizontal distance that the projectile may cover

Answer 1

Think carefully about the wording of this problem.  The function itself defines height, or how high the projectile goes.  You are asked about the maximum horizontal distance.  This is still a vertex problem, but once you find your x value, you want to double it, to get the up and down complete path.  

 

The x value of the vertex is just -b/(2a), where a and b are coefficients.  For this parabola, a=-1 and b=2, so your vertex occurs at -2/-2=1.  The maximum horizontal distance is thus 2 meters.