fozzzy wrote:
Attachment:
image 1.png
Which of the following inequalities specifies the shaded region to the left?
A. \(\sqrt{x^2+ 1}\)< 3
B. |2x - 3| < 5
C. |x + 1| > -1
D. x - 2 < 2
E. |x - 1| < 4
How to solve this question without plugging in values?
Using midpoint and distance, write an absolute value inequality in the form
|x - (midpoint)| < distance
1) Find the midpoint of the region, exactly halfway between -1 and 4, which is \(\frac{3}{2}\)
2) Find the distances of the endpoints from the midpoint
-1 is a distance of \(\frac{5}{2}\) from \(\frac{3}{2}\), and
4 is a distance of \(\frac{5}{2}\) from \(\frac{3}{2}\)
The distance cannot
equal \(\frac{5}{2}\) because the endpoints aren't included. The distance can be anything up to, but
less than, \(\frac{5}{2}\)
3. Set up the inequality
From above, the distance of x from the midpoint,* namely |x - \(\frac{3}{2}\)|, is < \(\frac{5}{2}\)
4. Write the inequality.
|x - (midpoint)| < distance
|x - \(\frac{3}{2}\)| < \(\frac{5}{2}\)
5. Find the answer that matches that inequality.
Eliminate C, which is always true (absolute value is always \(\geq0\), hence also always \(>-1\)), and D, which, without absolute value bars, does not cover two directions.
From the remaining choices: The answer must account for \(\frac{3}{2}\) somehow. There is only one answer with a 3 on LHS:
B) |2x - 3| < 5
That fits; just multiply all terms of the inequality derived from midpoint and distance by 2:
|x - \(\frac{3}{2}\)| < \(\frac{5}{2}\) (each term * 2)
|2x - 3| < 5
ANSWER B
*|x - (some number)| is the distance of x from (some number)
|x - 4| is the distance of x from 4
|x + 4| is the distance of x from -4
Blackbox, I'm not sure whether or not how I solved the problem is what you seek. I think it might be.
_________________
—The only thing more dangerous than ignorance is arrogance. ~Einstein—I stand with Ukraine.
Donate to Help Ukraine!