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Algebra 23 Online
OpenStudy (anonymous):

solve the equation. check for extraneous solutions. will fan and medal

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

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: \(81-72x =2x+3\) \(81-72x =-2x-3\)

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.

OpenStudy (anonymous):

78=74x?

OpenStudy (solomonzelman):

yes, so x=?

OpenStudy (anonymous):

74/78?

OpenStudy (solomonzelman):

yes

OpenStudy (anonymous):

what about in the second case?

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

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.

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)

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