Решение:
\[ y - f(x_0) = f'(x_0)(x - x_0) \]
\[ f(0) = 4(0) - \cos(0) + 1 \]
\[ f(0) = 0 - 1 + 1 = 0 \]
\[ f'(x) = \frac{d}{dx}(4x - \cos x + 1) \]
\[ f'(x) = 4 - (-\sin x) + 0 \]
\[ f'(x) = 4 + \sin x \]
\[ f'(0) = 4 + \sin(0) \]
\[ f'(0) = 4 + 0 = 4 \]
\[ y - 0 = 4(x - 0) \]
\[ y = 4x \]
Ответ: $$y = 4x$$