Given:
\[ \lim_{x \to \infty} \frac{f(7x)}{f(x)} = 1 \]
Since \( f \) is strictly increasing, we have:
\[ f(x) < f(5x) < f(7x) \]
This implies:
\[ \lim_{x \to \infty} \frac{f(5x)}{f(x)} = 1 \]
Then:
\[ \lim_{x \to \infty} \left[ \frac{f(5x)}{f(x)} - 1 \right] = 1 - 1 = 0 \]
Thus, the answer is: 0.
A body of mass 1000 kg is moving horizontally with a velocity of 6 m/s. If 200 kg extra mass is added, the final velocity (in m/s) is: