Asked by Danise

Describe how you know if an inequality is an “and” or an “or” problem. (use -3 < x+5 < 8). Also, how do you know if an absolute value question is an “and” or an “or” problem? Lastly, will you always have two solutions to an absolute value problem?

Answers

Answered by Reiny
first of all let's simplify the example
-3 < x+5 < 8
subtract 5 from each part

-8 < x < 3

In this notation, a < x < b, a is usually less than b
and x is any value "between" them.
As a matter of fact, I recall one text actually calling this the "between format", since we can read it as:
x lies between a and b
So the word "and" is always implied here
x > a AND x < b

if we were to say :
x > a OR x < b, then the entire number line would have to be included, which of course would not be true.

As to something like
|x| < 5
we have x < 5 ?? x > -5

Again, if we place OR between them, we get all the values of x
It must be AND to get the values of x between -5 and +5

In general, for
|stuff| < a, we have stuff < a AND stuff > -a, which is the same as:
-a < stuff < a

for
|stuff| > a , we have
stuff < -a OR stuff > a

If a > 0 , I cannot think of a case when there would not be two solutions.
If a < 0 , something like |stuff| < a would not make any sense, and there would be no solution.

There are no AI answers yet. The ability to request AI answers is coming soon!

Related Questions