Question

$25 \times {}^{2} - 81y {}^{2}$
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Answer 1

$25 {}^{2} \times - 81y {}^{2} = \\ - 81 \times 25 {}^{2} y {}^{2} = \\ \\ 25 {}^{2} = \\ 25 \times 25 = 625 \\ \\ - 81 \times 625y {}^{2} = \\ - (81 \times 625)y {}^{2} = \\ \\ - 50625y {}^{2}$