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Mathematics 18 Online
OpenStudy (kendalllarrson001):

help asap ! | y + 4 | < 1

OpenStudy (amking):

Are you graphing, plotting, or interval notation?

OpenStudy (kendalllarrson001):

none, just solving

OpenStudy (amking):

Okay. Well do you know your first step?

OpenStudy (kendalllarrson001):

i know the first step, i just need help w/ picking the answer. I did 1 minus -4 and my answer was -3. i just need to know why two of my answer choices are saying -3 < y < 5 and 5 < y < -3.

OpenStudy (amking):

What I usually do is plug in a number that satisfies the first answer choice into my original problem. Then, I do this with a number that satisfies my second answer choice. For example, first plug in 4 and check Then, plug in 6 and -2 and check.

OpenStudy (mathstudent55):

Don't take this the wrong way, but you don't know the first step. I'll explain it to you. An absolute value inequality with a \(\lt\) sign needs to be solved in a very specific way.

OpenStudy (mathstudent55):

To solve the absolute value inequality \(|X| \lt k\), where X is an expression containing a variable, and k is a non-negative number solve the compound inequality \(-k \lt X \lt k\)

OpenStudy (mathstudent55):

Now let's look at your case. Solve the absolute value inequality: | y + 4 | < 1 In this case, we see that y + 4 is the expression with a variable, and k is 4. We use the rule above and we change the absolute value inequality into the following compound inequality: \(-1 \lt y + 4 \lt 1\) Now we subtract 4 from all three sides: \(-5 \lt y \lt -3\)

OpenStudy (mathstudent55):

Do you see how it works?

OpenStudy (kendalllarrson001):

ooh, yeah i see now. my friend explained it to me differently and she made it seem complicated.

OpenStudy (kendalllarrson001):

thank you !

OpenStudy (mathstudent55):

This method is for absolute value inequalities with < or <=. If an absolute value inequality uses > or >=, then it's different. You need to use two inequalities separated by "or", not by "and."

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