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## Homework Statement

Positive point charges q and 2q are located at x=0 and x=3d respectively. What is the electric field at x=2d?

## Homework Equations

E=kQ/r^2

## The Attempt at a Solution

E1=kq/(2d)^2=kq/4d^2

E2=2kq/d^2

E1-E2=7kq/4d^2, to the left

To the left is correct but the answer is wrong :( can someone please tell me why? thanks.