Question

The axis of symmetry for the graph of the function f start bracket x end bracket equals one-quarter x square plus b x plus 10 is x=6. What is the value of b?

−12
−3

3

Answer 1

For a quadratic ax^2+bx+c the axis is x = -b/(2a). Here a = 1/4, so

6 = -b/(2·(1/4)) = -b/(1/2) = -2b.

Thus -2b = 6 ⇒ b = -3.