Question

2 (x² - 1 ) = x² + 7, com explicação please

Answer 1

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$2.(x {}^{2} - 1) = x {}^{2} + 7$

$2x {}^{2} - 2 = x {}^{2} + 7$

$2x {}^{2} - 2 - x {}^{2} - 7 = 0$

$x {}^{2} - 9 = 0 \\ x {}^{2} = 9$

$x = ( + ou - ) \sqrt{9} = + 3 \: \: e \: \: - 3$