Question

without actually calculating the cubes find the value of
$( {28}^{3} ) + ( - {15}^{3} ) + ( - {13}^{3} )$
please ans​

Answer 1

${28}^{3} - {15}^{3} - {13}^{3}$

$(15 + 13) ^{3} - ( {15}^{3} + {13}^{3} )$

$= 3(15)(13)(28)$

$= {2}^{2} \cdot {3}^{2} \cdot5 \cdot7 \cdot13$

$= 3 (13 + 2) \times 13 \times 28$

$=3(195)(28)$

$= 3(28)(28 \times 7 - 1)$

$= 3(784 \times 7 - 28)$

$= 3(5460) =16380$

Answer 2

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