Math Is Fun Forum

Karimazer1

Guest

URGENT Inequality Help

Hello. Really need help asap!

Ok, so I have x^2 >(or equal to) 6/11

So x>(or equal to)(root66 / 11) ... this i'm (semi)-sure of?

Howabout -root66 / 11. Does the inequality change sign? I know when dividing by negatives you changed the sign, but how about root?

Will it be, x>(or equal to)(-root66 / 11) as the second solution?

Please help

Karimazer1

Guest

Re: URGENT Inequality Help

It would really really help!

I have one last problem, which i've also been searching online for answer too, again regarding inequalities.

If I have

1/(1+x) >(and/or equal to, i can't find the little line to go underneath) 3/7

Am I correct in multiplying this across to solve?

I.e., 1>(3/7) + (3/7)x

so (1-(3/7))/(3/7) > x

Is this correct? I know this is so stupid, but I'm awful..it would really help to know if I'm on the right track. thanks in advance

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: URGENT Inequality Help

Hi Karimazer1

You cannot multiply an inequality by something for which you do not know if it is negative or positive. You should break up the problem into cases assuming 1+x to be positive and negative and see what happens in those two cases.

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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
The knowledge of some things as a function of age is a delta function.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: URGENT Inequality Help

Hi;

You know when you multiply by a negative number you reverse the inequality. Do you know what sign 1+x has?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: URGENT Inequality Help

hi Karimazer1

Have a look at

http://www.mathisfunforum.com/viewtopic.php?id=17749

Post #3 gives the basic approach to use.

At post #10 I slipped up and changed a sign so ended up doing a different question from the one asked.  The method still stands though.  Post #16 shows the correction.

For your question,  analyse the case 1 + x > 0 and the case 1 + x < 0 separately.

The symbols ≤ ≥  may be copied from the top of the page.

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: URGENT Inequality Help

Hi Bob

Didi you mean 1+x<0 ?

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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
The knowledge of some things as a function of age is a delta function.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: URGENT Inequality Help

Yes, thanks and well spotted.

You're a good proof reader and I sure need one.

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: URGENT Inequality Help

Thanks,but that is not true. Neither is.

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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
The knowledge of some things as a function of age is a delta function.