Select the x coordinate of the vertex of the parabola defined by the function: f(x)=-5x^2+3x+2 A. -5/3 B. 2 C. 3/10 D. -3/5 I keep coming up with 0. I know I have missed a step, please help. 1/12/2014 | Christine from Indianapolis, IN | 3 Answers | 0 Votes Mark favorite Subscribe Comment
Without calculus, the Horizontal Coordinate of a quadratic of f(x) =aX^2 + bx + c is equal to - b/ 2a Which in this case of f( X) = - 5 X^2 + 3X + 2 equals : - 3/[2(-5)] = -3/ -10 = 3/10 1/13/2014 | Parviz F. Comment
Hi Christine; f(x)=-5x^{2}+3x+2 The vertex is the point at which the change of y is zero. Therefore, we can take the first derivative of the function and calculate this... 0=-10x+3 -3=-10x 3/10=x ANSWER C 1/12/2014 | Vivian L. Comment
If you have a graphing calculator you can visually see that the answer is C. There is a formula derived from the quadratic formula for the x coordinate of the vertex which is -b/(2a) For any parabola it will give you the x coordinate of the vertex. f(x)=-5x^2+3x+2 a=-5, b=3, c=2 -3/(2*-5) = 3/10 The answer is C. 3/10 1/12/2014 | Varaia R. Comment