Question

Вычислите наиболее рациональным способом:
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Answer 1

Ответ:

$\frac{ {98}^{3} + {78}^{3} }{176} - 98 \times 78 = \\ \frac{(98 + 78)( {98}^{2} - 98 \times 78 + {78}^{2} )}{176} - 98 \times 78 = \\ {98}^{2} - 98 \times 78 + {78}^{2} - 98 \times 78 = \\ {98}^{2} - 2 \times 98 \times 78 + {78}^{2} = \\ {(98 - 78)}^{2} = {20}^{2} = 400$