# Homework Help: Line integral! uncertain about direction.

1. Feb 18, 2010

### aleee

1. The problem statement, all variables and given/known data
Evaluate $$\int[(3x-y)dx-xdy]$$ where C consist of the parabola y=x^2 from (0,0) to (1,1) and then the line segment from (1,1) to (0,1)

2. Relevant equations

3. The attempt at a solution
i did the integral of the y=x^2
parametrized
x=t
y=t^2
from 0 to 1
then i got my 1/2
but for the line segment do i just take the the integral using
x=t
y=1
but for the interval do i use 0 to 1 or 1 to 0

Last edited: Feb 18, 2010
2. Feb 18, 2010

### Dick

You want to go from (1,1) to (0,1) along (t,1). That makes it t=1 to t=0, right?

3. Feb 18, 2010

### aleee

so would i get $$\int_1^0\\(3t-1)dt$$
and would i just integrate it like that
i wouldnt require a negative because its a parametric correct?

4. Feb 18, 2010

### Dick

Sure. You don't have to add any extra signs. Just work out what it is and add it to your first path.

5. Feb 18, 2010

### aleee

thanks for the help!