# writing nested summation in full

I'm practising with precalculus exercises and came across this question of double summation. But I couldn't do it like a single sigma notation. Question is, how can I write this formulae in full to see what it does.

$$\sum_{i=1}^3 \sum_{j=1}^2 w_i x_j$$

• @PRCube $$= (w_1x_1 + w_1x_2) + (w_2x_1 + w_2x_2) + (w_3x_1 + w_3x_2)$$ – user137731 Oct 25 '16 at 3:11
Since $w_i$ is not depending on the inner sum, we can factor it out in (1).