# Solve the inequality 20-3y > y+4

• Sep 19th 2011, 03:26 AM
FailInMaths
Solve the inequality 20-3y > y+4
I am not sure of my workings but here it is:

$\displaystyle 20-3y = y+4$
$\displaystyle 20-4 = y+3y$
$\displaystyle 16=4y$
$\displaystyle y=4$

Therefore, $\displaystyle y>4$

Also, how do I illustrate the answer on a number line? Not quite sure what they are asking for
• Sep 19th 2011, 04:06 AM
TheChaz
Re: Solve the inequality 20-3y > y+4
Quote:

Originally Posted by FailInMaths
I am not sure of my workings but here it is:

$\displaystyle 20-3y > y+4$
$\displaystyle 20-4 > y+3y$
$\displaystyle 16>4y$
$\displaystyle y<4$

...

Also, how do I illustrate the answer on a number line? Not quite sure what they are asking for

The above is how it should read. Why did you switch to "=" ?
To graph y < 4
Mark "4" on a number line. Either circle it, or put a " ) " right parenthesis there, and then shade/draw a line to the left (where "lesser" numbrs are)
• Sep 19th 2011, 04:10 AM
FernandoRevilla
Re: Solve the inequality 20-3y > y+4
$\displaystyle 20-3y>y+4\Leftrightarrow 16>4y \Leftrightarrow 4>y$ so the solutions are the elements of $\displaystyle (-\infty,4)$ .

Edited: Sorry, I didn't see TheChaz's post.
• Sep 19th 2011, 04:10 AM
FailInMaths
Re: Solve the inequality 20-3y > y+4
Quote:

Originally Posted by TheChaz
The above is how it should read. Why did you switch to "=" ?
To graph y < 4
Mark "4" on a number line. Either circle it, or put a " ) " right parenthesis there, and then shade/draw a line to the left (where "lesser" numbrs are)

Oh, I get it now, thanks!
• Sep 19th 2011, 04:17 AM
TheChaz
Re: Solve the inequality 20-3y > y+4
Quote:

Originally Posted by FernandoRevilla
$\displaystyle 20-3y>y+4\Leftrightarrow 16>4y \Leftrightarrow 4>y$ so the solutions are the elements of $\displaystyle (-\infty,4)$ .

Edited: Sorry, I didn't see TheChaz's post.

No need for apologies, especially since you included the solution in interval notiation!