Quote:
Originally Posted by s_cianci  Distribute the cx(21 - x) to put it in polynomial form. The 'b' is then the coefficient in front of the 'x' term and the 'a' is the coefficient in front of the 'x^2' term. Calculate the specific value of -b/2a. |
While this gives you the location of a vertex, it does not tell you if that vertex is a maximum or a minimum. We need to take it one step further.
Lets follow s_cianci's instructions and distribute cx
=-cx^2+21cx)
The general form for a polynomial is
if your going to use the form
This part may get a little confusing, the c in your equation is not the same as the one in the general form.
your a=-c and b=21c because those are the coefficients in front of the
and
x
Now depending on your instructor you may or may not have to do the maximum test below, but you do have to somehow prove its a maximum, it's part of the question. If saying the coefficient is negative is sufficient then I would just stick with that!
Now test
values just to the left of
)
and
values just to the right of
. If both values just to the left of and to the right of
are both less than
, then we have a maximum.
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