You are Here: Home >< Maths

# increasing/decreasing function help? watch

1. solved
2. (Original post by katJ1873)
ok so I have a supposedly simple function but I can't seem to understand it;

y=x^(1.5)
dy/dx=1.5x^0.5

show y is an increasing function?

..so all values of x are meant to give a positive y values meaning it's increasing but I don't think it does? and how do I show this?

thanks
What level is this? A level, university? The answer will depend on what you already know.

Anyway, you need to show either that, for +ve x:

a) , or

b)

But the first is essentially trivial since the +ve square root is +ve by definition, and the second can be done by, say:

1. using the fact that is an increasing function (what is its derivative?).

2. considering, for , , rationalising the numerator using the difference-of-two-squares, and proceeding from there to show that the expression is +ve.
3. (Original post by atsruser)
What level is this? A level, university? The answer will depend on what you already know.

Anyway, you need to show either that, for +ve x:

a) , or

b)

But the first is essentially trivial since the +ve square root is +ve by definition, and the second can be done by, say:

1. using the fact that is an increasing function (what is its derivative?).

2. considering, for , , rationalising the numerator using the difference-of-two-squares, and proceeding from there to show that the expression is +ve.
it is a level - I think I understand now you said that, 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: November 11, 2017
The home of Results and Clearing

### 3,598

people online now

### 1,567,000

students helped last year
Today on TSR

Hang on, have Edexcel's come out already?

### University open days

1. SAE Institute
Animation, Audio, Film, Games, Music, Business, Web Further education
Thu, 16 Aug '18
2. Bournemouth University
Fri, 17 Aug '18
3. University of Bolton
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