Math Questions Help- Calculus!?

1. A particle is moving along the curve y=3sqrt(4x+4) . As the particle passes through the point(3,12) its -coordinate increases at a rate of 4 units per second. Find the rate of change of the distance from the particle to the origin at this instant.

2. Differential Equation Help Please!?

Solve the separable differential equation for

du/dt=e^(6u+2t)

Use the following initial condition:u(0)=-13 . u=?

It is not (-1/6) ln [-3e^(2t) + 3 + e^(78)]

3. Find the exact length of the polar curve described by: r=2e^.4theta on the interval [0,(1/6)]? Please write decimal answer to 5 places.