1. ## maxima minima help

heey guys how would I do these
1. The revenue from a company's product is given by R=180m+42m^2-m^3 where m is the output (per unit of time). Determine the output that will give maximum revenue.

2. An objet is projected into the air. The height of the object after t seconds is given by h=60t-5t^2
(I) what is the maximum height the object reaches?
(ii) how long after reaching the maximum height is the object 100m above its starting level?

for 2i I got 180m? is it right? dunno the rest

thank you all!

2. ## Re: maxima minima help

1. you find dR/dm (differentiate with respect to m), then let it equal to 0 and solve for m, make sure that the solution is positive.

2.i 180 is correct.

2ii) you have to solve the equation,

$60t-5t^2 = 100$

The answer has to be greater than 6 since it occurs after reaching the maximum height.

3. ## Re: maxima minima help

Originally Posted by integral95
1. you find dR/dm (differentiate with respect to m), then let it equal to 0 and solve for m, make sure that the solution is positive.

2.i 180 is correct.

2ii) you have to solve the equation,

$60t-5t^2 = 100$

The answer has to be greater than 6 since it occurs after reaching the maximum height.
thank you!!

4. ## Re: maxima minima help

Originally Posted by integral95
1. you find dR/dm (differentiate with respect to m), then let it equal to 0 and solve for m, make sure that the solution is positive.

2.i 180 is correct.

2ii) you have to solve the equation,

$60t-5t^2 = 100$

The answer has to be greater than 6 since it occurs after reaching the maximum height.
A piece of wire 20cm in length is bent to form a rectangle. Find the dimensions of the rectangle so as to enclose maximum area

5. ## Re: maxima minima help

Originally Posted by sssona09
A piece of wire 20cm in length is bent to form a rectangle. Find the dimensions of the rectangle so as to enclose maximum area
The perimeter of the rectangle is obviously 20cm. Let the sides be $x$ and $y$, and then find $y$ in terms of $x$. Once both sides are expressed in terms of $x$, you can obtain a formula for area which you can then differentiate.

For reference, your area formula should be $A = 10x-x^2$ (oops!).

6. ## Re: maxima minima help

Im learning too so i just planned to give it a try and post the working out for people who might need help

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