A printed page is to contain 60cm² of typing with clear margins around, of 5 by 3. Find the minimum area of the entire page?
$\displaystyle A=xy $
$\displaystyle 60=(x-3)(y-5) $
$\displaystyle \frac {60}{x-3}=y-5 $
$\displaystyle \frac {60}{x-3}+5=y $
$\displaystyle A=x(\frac {60}{x-3}+5)$
Can you do the rest? It's just a matter of taking the derivative of A and doing the first derivative test.
Oops, I forgot to take both sides into consideration
$\displaystyle A=xy $
$\displaystyle 60=(x-6)(y-10) $
$\displaystyle \frac {60}{x-6}=y-10 $
$\displaystyle \frac {60}{x-6}+10=y $
$\displaystyle A=x(\frac {60}{x-6}+10)$
Can you do the rest? It's just a matter of taking the derivative of A and doing the first derivative test.
mr fantastic's method works too, except I think he means y+6