Question:medium

If \(\int _{\alpha }^{2026-\alpha }\frac{(2026-x)^{2}}{x^{2}+(2026-x)^{2}}dx=100\), then \(\alpha =\)

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Use the property of replacing x by a + b - x and add the two integrals.
Updated On: Nov 12, 2026
  • \(913\)
  • \(1013\)
  • \(1113\)
  • \(1213\)
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Observe the Symmetry
The two fractions $\dfrac{x^{2}}{x^{2}+(2026-x)^{2}}$ and $\dfrac{(2026-x)^{2}}{x^{2}+(2026-x)^{2}}$ add up to $1$.

Step 2: Use the Limits
The interval is symmetric about $x=1013$, so both integrals are equal and each is half the integral of $1$, i.e. $\dfrac{2026-2\alpha}{2}$.

Step 3: Solve
$1013-\alpha=100$, so $\alpha=913$.

Final Answer:
Solving 1013 - alpha = 100 gives alpha = 913. \[ \boxed{\text{(A) }913} \]
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