Hello, Sreeram,
I note that at t = 0, the velocity of the particle is 1 ft/min, not 0. Odd, but true, the equation claims. It's velocity at 2 is 9 feet/min. Then average velocity over the 2 minutes is (1 + 9)/2 = 5 ft/min. Times the 2 minutes between 0 and 2, it travels 10 feet.
I might be wrong, but the equation has this pesky 1 attached to the end. I read that as it has a velocity of 1 from the start.
Bob