Three point charges are aligned along the x-axis as shown in Figure. Find the electric field at the position x = 2.0 m, y = 0 m.


Three point charges are aligned along the x-axis as shown in Figure

You need question yourself about one and only one thing: What electric field is present here?. The answer for this question it's simple: The sum or superposition of all electric field caused by each electric charge. Therefore, just find the electric field for each individual electric charge and then, sum his expression to find the answer.
redraw the image for establish the adequate distance to field point, from each source point:

Now, write an expression of each electric field:

The last step is sum the electric field expressions:

Replace the values of electric charge and distance to get the final answer:

our final answer is:

Problems like this are very common on quick test and homeworks, the uniques changes are the electric charges distribution (like triangle, rectangle or whatever ) and the number of electric charge. You only need identify the distance from each electric charge to field point, and then follow the steps shown on this post.
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