What is the axis of symmetry of the function f(x) = -(x+9)(x-21)

x = 6

Step-by-step explanation:

Take  f(x) = -(x+9)(x-21)  and multiply it out.  We get:

          f(x) = -[x^2 + 9x - 21x - 189], or

          f(x) = -x^2 + 12x + 189

This is a quadratic equation.  The coefficients are a = -1, b = 12 and c = 189.

The equation of the axis of symmetry is x = -b/(2a), which here equals:

x  =  -12 / [2*(-1)], or x = 6.

nope.   happens to me as well.

-aparri