You are Here: Home >< Maths

# C1 Optimisation help watch

1. I need some help with this question:

"The sum of two positive integers is 40. Find the two integers such that the product of the square of one number and the cube of the other number is a maximum."

I tried to do this question but didn't get very far:

then:

Do I need to solve this for 0, or is there an easier way?
2. (Original post by arniebob)
I need some help with this question:

"The sum of two positive integers is 40. Find the two integers such that the product of the square of one number and the cube of the other number is a maximum."

I tried to do this question but didn't get very far:

then:

Do I need to solve this for 0, or is there an easier way?
just solve dp/dy = 0 to find suitable y then work out x
3. (Original post by arniebob)

Do I need to solve this for 0, or is there an easier way?
That all looks fine. Yes, solve dP/dy = 0 which is easier than it looks - you can divide through by 5, and also be y^2, as you are told that y is not zero (because it is positive). You'll get two answers, and you'll have to explain why you reject one of them.
4. (Original post by Pangol)
That all looks fine. Yes, solve dP/dy = 0 which is easier than it looks - you can divide through by 5, and also be y^2, as you are told that y is not zero (because it is positive). You'll get two answers, and you'll have to explain why you reject one of them.
Ah I see, thanks!

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: October 27, 2016
The home of Results and Clearing

### 3,454

people online now

### 1,567,000

students helped last year
Today on TSR

### IT'S TODAY!

A-level results chat here

### University open days

1. Bournemouth University
Fri, 17 Aug '18
2. University of Bolton
Fri, 17 Aug '18
3. Bishop Grosseteste University
Fri, 17 Aug '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams