# Simple problem

1. Mar 27, 2007

### Weave

1. The problem statement, all variables and given/known data
A particle is moving along the curve $$y= 3 \sqrt(4 x + 4)$$. As the particle passes through the point (3, 12), its x-coordinate increases at a rate of 2 units per second. Find the rate of change of the distance from the particle to the origin at this instant.

2. Relevant equations
1.$$y= 3* \sqrt(4 x + 4)$$

3. The attempt at a solution
Not too sure how to start.

2. Mar 27, 2007

### pki15

Begin with a formula for the distance(D) from (x,y) to the origin. Then you can plug in what you know about y. Finally differentiate (implicitly) the formula with respect to time. You should get an equation involving dD/dt, x, and dx/dt. You know x, and dx/dt. Find dD/dt.

3. Mar 28, 2007

### Weave

What formula for distance are you talking about?

4. Mar 28, 2007

### HallsofIvy

No wonder you are having a problem! When dealing with "distance to the origin", you really need to know that the distance from a point (x,y) to the origin, (0,0), is $\sqrt{x^2+ y^2}$!