3. Решите уравнение: a) 5²-x²=0 б) 9-36y² = 0 в) (5-у)²-у(у+2,5)=25

a) \(5^2 - x^2 = 0\) \((5 - x)(5 + x) = 0\) \(5 - x = 0\) или \(5 + x = 0\) \(x = 5\) или \(x = -5\) б) \(9 - 36y^2 = 0\) \(36y^2 = 9\) \(y^2 = \frac{9}{36} = \frac{1}{4}\) \(y = \pm \sqrt{\frac{1}{4}} = \pm \frac{1}{2}\) в) \((5 - y)^2 - y(y + 2.5) = 25\) \(25 - 10y + y^2 - y^2 - 2.5y = 25\) \(-12.5y = 0\) \(y = 0\)