Решите уравнения.номер 3

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а)
$x {}^{2} = 0.64 \\ x1 = 0.8 \\ x2 = - 0.8$

б)
$3x {}^{2} - 7 = 14 \\ 3x {}^{2} = 21 \\ x {}^{2} = 7 \\ x1 = \sqrt{7} \\ x2 = - \sqrt{7}$

в)
$(x + 7) {}^{2} = 36 \\ x {}^{2} + 14x + 49 = 36 \\ x {}^{2} + 14x + 13 = 0 \\ \\ x1.2 = \frac{ - 14 + - \sqrt{14 {}^{2} - 4 \times 13 \times 1 } }{2} \\ \\ x1.2 = \frac{ - 14 + - 12}{2} \\ \\ x1 = - 13 \\ x2 = - 1$

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