IIT JEE 1983 Maths - MCQ Question 18

Algebra Level 3

If x x satisfies x 1 + x 2 + x 3 6 |x-1|+|x-2|+|x-3|\geq6 , then which option is correct?


In case you are preparing for IIT JEE, you may want to try IIT JEE 1983 Mathematics Archives .
0 x 4 0≤x≤4 x 0 x≤0 or x 4 x≥4 x 2 x≤-2 or x 4 x≥4 None of the others

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1 solution

Deepanshu Jindal
Mar 29, 2020

f(x) = |x-1| + |x-2| + |x-3|

f(x) = { 6 3 x x 1 r a n g e ( 3 , inf ) 4 x 1 x 2 r a n g e ( 0 , 2 ) x 2 x 3 r a n g e ( 2 , 2 ) 3 x 6 3 x r a n g e ( 3 , inf ) \begin{cases} 6-3x & x\leq 1 & range(3,\inf)\\ 4-x & 1\leq x\leq 2 & range(0,2)\\ x & 2\leq x\leq 3 & range(2,2)\\ 3x-6 & 3\leq x & range(3,\inf) \end{cases}

The only regions which we need to analyze are x<1 and x>3.

By plotting the function we can see that x 0 x\leq 0 and x 4 x\geq 4 are the desired regions.

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