How Does Quadrant Location Affect the Electric Field Vector Calculation?

[azizlwl]

Homework Statement

From attachment R=-xa_a-ya_y+3a_z

Homework Equations

The Attempt at a Solution

I see 4 different values, one for each quadrant.
1st.quadrant
R=+xa_a-ya_y+3a_z
2nd. quadrant
R=-xa_a+ya_y+3a_z
3rd.
R=-xa_a+ya_y+3a_z
4th
R=-xa_a-ya_y+3a_z

Where did I go wrong in determine value of R?

 

[Chestermiller]

The equation they gave applies to all 4 quadrants. It is just equal to minus a position vector drawn from the origin to any arbitrary point (x,y,-3) on the square sheet. The 3 unit vectors in their equation are pointing in the 3 positive coordinate directions.

Chet