Пусть прямая y = kx + b - искомая общая касательная к графикам функций. x1 и x2 - абсциссы соответствующих точек касанияy = f(x0) + f'(x0) (x - x0) = f'(x0) * x + f(x0) - f ' (x0)*x0f ' (x0) = tga = k k = p ' (x1) = g ' (x2)p ' (x) = 2x + 4, p '(x1) = 2x1 + 4g ' (x) = 2x + 8, g'(x2) = 2x2 + 8 2x1 + 4 = 2x2 + 8 x1 + 2 = x2 + 4b = p(x1) - p ' (x1)*x1 = x1^2 + 4x1 + 8 - (2x1 + 4)*x1 = = x1^2 + 4x1 + 8 - 2x1^2 - 4x1 = - x1^2 + 8b = g(x2) - g'(x2) * x2 = x2^2 + 8x2 + 4 - (2x2 + 8)*x2 = = x2^2 + 8x2 + 4 - 2x2^2 - 8x2 = - x2^2 + 4 - x1^2 + 8 = - x2^2 + 4Решим системуx1 + 2 = x2 + 4- x1^2 + 8 = - x2^2 + 4x1 - x2 = 2x1^2 - x^2 = 4x1 - x2 = 2(x1 - x2)(x1 + x2) = 4x1 - x2 = 22*(x1 + x2) = 4x1 - x2 = 2x1 + x2 = 2------------------- + 2x1 = 4x1 = 2x2 = 2 - x1 = 2 - 2 = 0 k = p '(x1) = 2x1 + 4 = 2*2 + 4 = 4 + 4 = 8b = - x1^2 + 8 = - 2^2 + 8 = 8 - 4 = 4Получаемy = 8x + 4