Solve the following inequality

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February 20th 2011, 05:19 AM
hoanghai549

Solve the following inequality

(3a+7)/(a+4) >= 0

I forgot the step to solve the problem , please help me !!!(Crying)
February 20th 2011, 05:35 AM
Plato

Quote:

Originally Posted by hoanghai549

(3a+7)/(a+4) >= 0

You want to insure that both of $3a+7\ge0~\&~a+4>0$ are true
or both $3a+7\le0~\&~a+4<0$ are true.
February 20th 2011, 05:41 AM
hoanghai549

So It means I have to solve the two above conditions or just use the one thing ?
February 20th 2011, 05:52 AM
Plato

Quote:

Originally Posted by hoanghai549

So It means I have to solve the two above conditions or just use the one thing ?

There will be two different intervals in the solution set.
So solve both and unite.
February 20th 2011, 05:54 AM
hoanghai549

nice thanks for your help
February 20th 2011, 07:14 AM
Archie Meade

deleted
February 20th 2011, 03:45 PM
Plato

Quote:

Originally Posted by hoanghai549

(3a+7)/(a+4) >= 0

Look at the numerator and the denominator.
If both have the same sign then the inequality is true.
It is easy to see that if $a<-4$ then both are negative.
If $a\ge -\frac{7}{3}$ then both are non-negative.

Write the solution set as $(-\infty,-4)\cup\left[-\frac{7}{3},\infty\right)$ .

There is no complicated calculation necessary.

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