# Math Help - a maths problem has to do with derivatives

1. ## a maths problem has to do with derivatives

cant figure the last part the examiner says answer is 72 answer to (i) is y/(6(48-8x)

2. ## Re: a maths problem has to do with derivatives

Take the expression for the area in (ii) and find the derivative, set to zero. Find the value of x for this. Now, take the second derivative and show that the function is concave down (so it looks like a hill, not a valley, and so has a maximum). Now that you've shown this, you can take the x-value you found above and substitute back into the area expression.