# Math Help - Vectors

1. ## Vectors

Unsure where to start here really.

The forces F1 = (ai - 2aj)N and F2 = (2i + 4j)N act on a particle. The resultant of F1 + F2 has magnitude 4N. Find the possible values of a.

Thanks for any help

2. ## hi

Hi

You know how to add the vectors?
And how to take the magnitude?

F1+F2=(a+2)i + (4-2a)j

$(a+2)^2 + (4-2a)^2 = 16$
Now solve for a.