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jimthompson5910 (jim_thompson5910):
First we must divide both sides by 3
3|3k| = 27
|3k| = 27/3
|3k| = 9
jimthompson5910 (jim_thompson5910):
Then we use the idea that if |x| = p, then x = p or x = -p to go from this equation
|3k| = 9
to these two equations
3k = 9 or 3k = -9
jimthompson5910 (jim_thompson5910):
solve those last two equations to get your two answers
OpenStudy (anonymous):
9
jimthompson5910 (jim_thompson5910):
3k = 9, so k = ??
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jimthompson5910 (jim_thompson5910):
3k means "3 times k"
OpenStudy (tkhunny):
\(3|3k| = 27\)
Divide by 3
\(|3k| = 9\)
Figure out that 3 is positive and the absolute values do nothing
\(3|k| = 9\)
Divide by 3
\(|k| = 3\)
Easier yet?
OpenStudy (anonymous):
how do you get 27
OpenStudy (tkhunny):
?? From the problem statement?
OpenStudy (tkhunny):
Do you mean to say some answer key says a solution is k = 27? That would be incorrect.
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OpenStudy (anonymous):
yea.
OpenStudy (tkhunny):
AS WRITTEN, we have k = 3 or k = -3.
jimthompson5910 (jim_thompson5910):
think of 3k = 9 as a statement saying
"3 times _____ equals 9"
what goes in the blank?
OpenStudy (anonymous):
k ?
jimthompson5910 (jim_thompson5910):
yes, but what number also goes in the blank in place of k?
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jimthompson5910 (jim_thompson5910):
3 times SOME NUMBER equals 9
what replaces "SOME NUMBER" ?
OpenStudy (anonymous):
- 3 ?
jimthompson5910 (jim_thompson5910):
why is it negative?
jimthompson5910 (jim_thompson5910):
3 times -3 is positive 9 ? that's a true statement?
OpenStudy (anonymous):
no ?
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jimthompson5910 (jim_thompson5910):
it's not
jimthompson5910 (jim_thompson5910):
it should be 3 times 3 = 9
jimthompson5910 (jim_thompson5910):
so the solution to 3k = 9 is k = 3
jimthompson5910 (jim_thompson5910):
in a very similar fashion, the solution to 3k = -9 is k = -3
jimthompson5910 (jim_thompson5910):
Another way to see that k = 3 is the solution to 3k = 9 is to divide both sides of 3k = 9 by 3 to isolate k
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OpenStudy (anonymous):
\[{-3 , 9 }\] ?
jimthompson5910 (jim_thompson5910):
I don't know what you mean there. Are you saying the two answers are k = -3 and k = 9 ?
OpenStudy (anonymous):
yea.
jimthompson5910 (jim_thompson5910):
that's not correct
jimthompson5910 (jim_thompson5910):
how did you get k = 9?
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OpenStudy (anonymous):
study guide , help
jimthompson5910 (jim_thompson5910):
do you see how I got 3k = 9 and 3k = -9 ?
OpenStudy (anonymous):
no , i really suck at math
jimthompson5910 (jim_thompson5910):
go back to my steps and tell me where you got stuck
OpenStudy (anonymous):
Then we use the idea that if |x| = p, then x = p or x = -p to go from this equation |3k| = 9 to these two equations 3k = 9 or 3k = -9
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OpenStudy (anonymous):
that part
jimthompson5910 (jim_thompson5910):
that rule allows us to say things like
|x| = 7 turns into x = 7 or x = -7
jimthompson5910 (jim_thompson5910):
or if |x| = 3, then x = 3 or x = -3
jimthompson5910 (jim_thompson5910):
|x| = 3 means that some number x is 3 units away from zero
The numbers 3 and -3 are both 3 units away from zero, which is why the two answers to |x| = 3 are x = 3 or x = -3
jimthompson5910 (jim_thompson5910):
so if I had |x| = 5, then what are the two solutions to x?
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OpenStudy (anonymous):
|x| = 5 or |x| = -5 ?
jimthompson5910 (jim_thompson5910):
no, it should be x = 5 or x = -5
those two numbers are five units away from zero (on the number line)
jimthompson5910 (jim_thompson5910):
absolute value is basically "distance the number is from zero on the number line"
jimthompson5910 (jim_thompson5910):
what about something like |x| = 14
what are the two solutions to x?