Minimum?

Algebra Level 3

Find the minimum value of the following expression:

x 1 + x 2 + x 3 + x 4 + x 5 . \large \left|x - 1\right| + \left|x - 2\right| + \left|x - 3\right| + \left|x - 4\right| + \left|x-5\right| .

Notation : | \cdot | denotes the absolute value function .


The answer is 6.

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1 solution

谦艺 伍
Jul 13, 2016

The question is equivalent to finding a point x x on number line such that the sum of distance between x x and 1, 2, 3, 4, 5 is minimized.

Notice that the sum of distance between x x and 1, and between x x and 5 is minimized when x x is between 1 and 5. In that case, the sum of distance between x x and 1, and between x x and 5 is equal to 5 1 = 4 5-1=4 .

Also notice that the sum of distance between x x and 2, and between x x and 4 is minimized when x x is between 2 and 4. In that case, the sum of distance between x x and 2, and between x x and 4 is equal to 4 2 = 2 4-2=2 .

Besides, notice that the distance between x x and 3 is minimized when x = 3 x=3 .

Since the location of x x which minimized the sum of distance in the above three cases intersect at x = 3 x=3 , x = 3 x = 3 minimize the given expression.

So, the minimum value is 2 + 1 + 0 + 1 + 2 = 6 2+1+0+1+2 = 6 .

Thank you for telling me

Shashwat Dhurandhar - 3 years, 9 months ago

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