Math Is Fun Forum

Marisca

Member

Registered: 2011-04-22

Posts: 53

Families of functions help needed!

Find {x:x^3/2 > x^2}

I Have no idea how to do this, please help!

Last edited by Marisca (2012-03-10 14:21:16)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Families of functions help needed!

hi Marisca,

A graph will show you the answer but an algebraic solution is usually required as well.

Now is two expressions multiply to give zero either they are both positive or they are both negative, so

OR

Can you finish this from here? 

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Families of functions help needed!

hi Marisca

You can use the splitting into two parts as Bob suggested,but here's another method:

We can divide by x^2 because it's always positive! and because 0 is not the solution of the inequality which we can check by plugging it in.If these two conditions were not satisfied we would be able to do this.

If you have more questions be free to ask here.

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
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Marisca

Member

Registered: 2011-04-22

Posts: 53

Re: Families of functions help needed!

Yes, I could finish it from there.
Thanks a lot, really helped me