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The solution of the inequality

\frac{\left ( x+1 \right )\left ( x-1 \right )^{4}}{\left ( x-3 \right )^{2}\left ( x-2 \right )}\geq 0  is

Option: 1

\left ( -\infty,-1 \right )\cup \left ( 2,\infty\right )


Option: 2

\left ( -\infty ,-1\right ]\cup \left ( 2,\infty \right )


Option: 3

\left ( -\infty,-1 \right ] \cup \left ( 2,\infty \right )\cup \{1\}


Option: 4

none of these


Answers (1)

best_answer

1. 0 is on one side

2. All linear factors

3. Coefficients of x are positive

4. Critical points

    x+1=0\Rightarrow x=-1\\

    x-2=0\Rightarrow x=2\\

(Do not include x-1=0\Rightarrow x=-1\\ and x-3=0\Rightarrow x=3, as they have even powers)

5. Draw number line and mark critical points on it

6. Mark (+) sign on RHS and write alternate signs towards left

7. We need x for which expression is (+)ve, so all numbers from -\infty\: to\: -1\\ and from 2\: to\: \infty are to be included in the answer

8. Now check at all critical points (including ones with even powers)

  At x=-1 expression is 0, so included in the answer

  At x=1 expression=0, so included

  At x=3, expression is not defined (as denominator = 0), so excluded

  At x=2, expression is not defined , so excluded.

9. Answer is \left ( -\infty,-1 \right )\cup \left ( 2,\infty \right )\cup \{-1,1\}\\

              = \left ( -\infty,-1 \right ]\cup \left ( 2,\infty \right )\cup \{1\}

 

Posted by

Shailly goel

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