The value of \({1}^{3}-{2}^{3}+{3}^{3}-\ldots +{15}^{3}\) is: [JEE Main 2026, 6 Apr (Shift 1)]
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The value of \({1}^{3}-{2}^{3}+{3}^{3}-\ldots +{15}^{3}\) is:
[JEE Main 2026, 6 Apr (Shift 1)]
✓ Correct answer: b)
\(1856\)
Explanation
\(S=1^3-2^3+3^3-\ldots+15^3\)
\(=\left(1^3+2^3+\ldots+15^3\right)-2\left(2^3+4^3+\ldots+14^3\right)\)
\(=\left(1^3+2^3+\ldots+15^3\right)-2^4\left(1^3+2^3+\ldots+7^3\right)\)
\(=\left[\frac{15 \times 16}{2}\right]^2-16\left[\frac{7 \times 8}{2}\right]^2\)
\(=14400-16\times 784\)
\(=14400-12544\)
\(=1856\)
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