0
$\begingroup$

here is the question:

enter image description here

here is the correct answer:

(-1, 7/2)

My working:

I know that by plugging in 0 into the equation you get -1 but I don't understand how to get 7/2

thank you

$\endgroup$
2
$\begingroup$

Hint: $f(x) = -2(x-\frac32)^2 + \frac72$. So the maximum is when the quadratic term is zero.

$\endgroup$
  • $\begingroup$ where did 3/2 come from? $\endgroup$ – Cash Vai Dec 6 '13 at 14:09
  • $\begingroup$ That's needed to complete the square. Try a few exercises in that, you will get good at finding the appropriate value. $\endgroup$ – Macavity Dec 6 '13 at 14:34
0
$\begingroup$

HINT:

Apply the second derivative test to get minima/maxima of the function. Don't forget to check the boundaries of the interval.

$\endgroup$
0
$\begingroup$

You don't need derivatives at all. The only candidates for min and max are clearly $0$, $2$ and $3/2$.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.