Algebra
23 Online
OpenStudy (anonymous):
solve the equation. check for extraneous solutions. will fan and medal
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OpenStudy (anonymous):
\[9\left| 9-8x \right|=2x+3\]
OpenStudy (solomonzelman):
well, you will get two results:
\(9\left| 9-8x \right|=2x+3\)
\(9(9-8x )=2x+3\) OR \(9(9-8x )=-2x-3\)
OpenStudy (solomonzelman):
solve each case individually.
OpenStudy (anonymous):
i dont know where to start. will you walk me through it?
OpenStudy (solomonzelman):
well, expand the right side in case 1
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OpenStudy (solomonzelman):
I mean the left side (not the right side)
OpenStudy (anonymous):
would you move the x to the left side first?
OpenStudy (solomonzelman):
\(9(9-8x )=2x+3\)
\(9\cdot9-9\cdot8x =2x+3\)
\(81-72x =2x+3\)
OpenStudy (solomonzelman):
So in case two you would have the same, but the right side would be -2x-3
OpenStudy (solomonzelman):
Solve for each:
\(81-72x =2x+3\) \(81-72x =-2x-3\)
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OpenStudy (anonymous):
x would go on the left side?
OpenStudy (solomonzelman):
you can add 72x to both sides in case 2 and case 1
OpenStudy (anonymous):
leaving us with 81=74x+3
OpenStudy (solomonzelman):
two cases:
\(81-72x =2x+3\)
\(81-72x+72x =2x+72x+3\)
\(81=74x+3\)
right!
OpenStudy (solomonzelman):
then subtract 3 from both sides.
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OpenStudy (anonymous):
78=74x?
OpenStudy (solomonzelman):
yes, so x=?
OpenStudy (anonymous):
74/78?
OpenStudy (solomonzelman):
yes
OpenStudy (anonymous):
what about in the second case?
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OpenStudy (solomonzelman):
Now in case 2:
\(81-72x =-2x-3\)
OpenStudy (solomonzelman):
you also add 72x to both sides,
THEN, add 3 to both sides
OpenStudy (anonymous):
x=70/84?
OpenStudy (solomonzelman):
oh the first one is incorrect, and this one too
OpenStudy (anonymous):
noooo
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OpenStudy (solomonzelman):
when in case one you have:
78=74x
you divide by 74 on both sides, and thus
x=78/74 (not 74/78)
OpenStudy (solomonzelman):
And in case two you made the same mistake
OpenStudy (anonymous):
so it would be 84/70?
OpenStudy (solomonzelman):
Yes, for case 2.
OpenStudy (solomonzelman):
And they are not extraneous.
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OpenStudy (solomonzelman):
let me say correctly what would have been extraneous:
OpenStudy (solomonzelman):
Any x-solution, in this case, that is equal to \(C\) that satisfies:
\(C<-2/3\)
OpenStudy (solomonzelman):
because if x is less than -2/3
then 2x+3 is negative, and absolute value can NOT e equal to negative
(since absolute value is really a distance)