Question

A quadratic function f(x) = x^2 + bx +C has a vertex at (−2,1). Find the values of a, b and c. Show your work describe the strategy used.

Answer 1

• a = 1, b = 4, c = 5

Explanation:

The x-coordinate of the vertex is determined by:

• x = -b/(2a)

So we have:

• -2 = -b/(2a)
• b = 4a = 4 since a = 1 (x² has no coefficient, so its 1)

Now, substitute x- and y- values to find the value of c:

• 1 = (-2)² + 4(-2) + c
• 1 = 4 - 8 + c
• 1 = -4 + c
• c = 1 + 4
• c = 5