Effective spring constant of two springs latched headon

In the Princeton Review for AP Physics, there is a question on calculating the effective spring constant when two springs are joined side by side, like so:

spring 1 spring 2
|~~~~~~ ~~~~~~[mass]

Their spring constants are k1 and k2.

How would you go about answering the question? The book starts by saying F = -k1/x1 and F = -k2/x2, where F is the net force, and x1 and x2 are the displacements for each spring, but this does not seem right to me. Is it?

Thanks!