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The numerator of the fraction is x, while the denominator is 5 more the numerator.
if the value of the fraction is less than 2/5, find the value of x
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Let x be the numerator; then the denominator is (x+5) and the fraction is .
They want you solve this inequality
< . (1)
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| Attention (!) |
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Do not multiply both sides by (x+5), because you don't know in advance,
if this value is positive or negative.
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| THERE IS ANOTHER METHOD TO SOLVE IT without making wrong steps ! |
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Re-write equation (1) equivalently in this form
- < 0.
Write it with the common denominator, which is 5*(x+5).
- < 0.
Simplify
< 0,
< 0,
< 0.
This inequality is equivalent to
< 0.
The last inequality is hold in these two cases:
(a) 3x-10 < 0 and x+5 > 0
or
(b) 3x-10 > 0 and x+5 < 0.
In case (a), it implies 3x < 10 and x > -5, which is the same as x < 10/3 and x > -5,
which gives the answer -5 < x < 10/3.
In case (b), it implies 3x > 10 and x < -5, which has no solutions.
ANSWER. The solution set is -5 < x < 10/3, or, in interval form, (-5, 10/3).
Solved.