Calculating Rate of Change of Distance to Origin

[Weave]

Homework Statement

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.

Homework Equations

1.y= 3* \sqrt(4 x + 4)

The Attempt at a Solution

Not too sure how to start.

 

[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.

 

[Weave]

What formula for distance are you talking about?

 

[HallsofIvy]

What formula for distance are you talking about?

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}!