Find the solution set for ( 2 x − 1 ) ( x + 5 ) ≤ 3 . Note :- Careful, scope for silly mistakes !
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Nice technique !
Observe that when the denominator is an algebraic expression, we need to consider 2 cases :- denominator positive and denominator negative. After considering both cases, we need to take the most appropriate solution set of the variable that satisfy both cases.
You have not included 0 . 5 in the correct option. I think it should be included.
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At 0.5, the expression on left hand side of the given inequality becomes undefined !
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Yes, I had my doubt clarified by Abhineet.
Thanks.
Your solution picture is titled. Straightening it would provide a better view.
:)
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@Soumo Mukherjee – Actually when I upload any pic to brilliant, the pic is getting tilted. Did you mean titled or tilted ?
No, actually not...Look, if you put x = 0 . 5 , then the denominator tends to infinity which is not accepted...and as a result 0 . 5 is not taken as a solution.
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yeah, I overlooked that. Actually I used method of interval. So the transformed expression had an extraneous root: 0 . 5
thanks :)
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@Soumo Mukherjee – Oh okay...well, no problem!:) anytime...
Sorry guys, I dont know latex, except the very basics and so I couldnt write the whole solution in latex. Is the picture clear ?
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2 x − 1 x + 5 ≤ 3 ⇔ 2 x − 1 x + 5 − 3 ( 2 x − 1 ) ≤ 0 ⇔ 2 x − 1 − 5 x + 8 ≤ 0
We have this table:
\begin{array}{*{20}{c}} \hline & x & & {\left( { - \infty ,\displaystyle\frac{1}{2}} \right)} & {\displaystyle\frac{1}{2}} & {\left( {\displaystyle\frac{1}{2},\displaystyle\frac{8}{5}} \right)} & {\displaystyle\frac{8}{5}} & {\left( {\displaystyle\frac{8}{5}, + \infty } \right)} & \\ \hline & { - 5x + 8} & & + & + & + & 0 & - & \\ \hline & {2x - 1} & & - & 0 & + & + & + & \\ \hline & {\displaystyle\frac{{ - 5x + 8}}{{2x - 1}}} & & - & {||} & + & 0 & - & \\ \hline \end{array}
As shown in this table, the solution set is ( − ∞ , 2 1 ) ∪ [ 5 8 , + ∞ )