3. Решите уравнение: a) 82- x²= 0 б) 36y² – 25 = 0 в) (5-x)²-x(x+6,5)=25

Решение: а) $81 - x^2 = 0 Rightarrow x^2 = 81 Rightarrow x = \pm 9$ б) $36y^2 - 25 = 0 Rightarrow 36y^2 = 25 Rightarrow y^2 = \frac{25}{36} Rightarrow y = \pm \frac{5}{6}$ в) $(5 - x)^2 - x(x + 6.5) = 25 Rightarrow 25 - 10x + x^2 - x^2 - 6.5x = 25 Rightarrow -16.5x = 0 Rightarrow x = 0$