Question:medium

Find the value of \(\displaystyle\int_{1}^{4}\big(|x-1|+|x-2|+|x-3|\big)\,dx\).

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Split at x=1,2,3 and simplify the sum of absolute values on each piece before integrating.
Updated On: Sep 23, 2026
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Solution and Explanation

Step 1: Reframing using distance-from-point intuition:
Each \(|x-k|\) is the distance from \(x\) to \(k\); summing three such distances and integrating is equivalent to computing three separate simple absolute-value integrals and adding them.

Step 2: Splitting into three separate standard integrals:
\(\displaystyle\int_1^4|x-1|dx+\int_1^4|x-2|dx+\int_1^4|x-3|dx\), each evaluated independently by splitting at its own single breakpoint.

Step 3: Evaluating each one:
\(\int_1^4|x-1|dx=\int_1^4(x-1)dx=\tfrac{9}{2}\) (no sign change, \(x\ge1\) throughout). \(\int_1^4|x-2|dx=\int_1^2(2-x)dx+\int_2^4(x-2)dx=\tfrac12+2=\tfrac52\). \(\int_1^4|x-3|dx=\int_1^3(3-x)dx+\int_3^4(x-3)dx=2+\tfrac12=\tfrac52\).

Step 4: Summing the three results:
Total \(=\tfrac92+\tfrac52+\tfrac52=\tfrac{9+5+5}{2}=\tfrac{19}{2}\), matching the piecewise method.

Final Answer:
\[ \boxed{\dfrac{19}{2}} \]
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