Question

2) x² - (9 - x)² > -2x;


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Answer 1

$x {}^{2} - (9 - x) {}^{2} > - 2x \\ x {}^{2} - (81 - 18x + x {}^{2} ) > - 2x \\ x {}^{2} - 81 + 18x - x {}^{2} > - 2x \\ - 81 + 18x > - 2x \\ 18x + 2x > 81 \\ 20x > 81 \\ x > \frac{81}{20}$