Select the x-coordinate of the vertex of the parabola defined by the function

Question

f(x) = -5x^2 + 7x + 5.?

A. - 5/7 

B. 5 
C. 7/10 
D. -7/5

Answer 1

The function f(x) = - 5x² + 7x + 5

y = - 5x² + 7x + 5

Compare it to parabola equation y = ax² + bx + c

a = -5, b = 7, c = 5

The x coordinate of vertex is axis of symmetry x = -b/2a

x = -7/2(-5)

x = 7/10

Therefore the x coordinate of vertex of the parabola is x = 7/10.

Option (c) is the correct answer.