We can know that the vector F 1+F2+F3=( 1-2+3), (2+3-4), (3-4+5) = (2, 1, 4) = f.
Finding the resultant force is actually finding the vector f (2, 1, 4).
This algorithm is simpler than modeling, which is also the most basic and practical way of space vector. Save a lot of trouble caused by vector module and modeling.
Find out the spatial coordinates of the F junction, and you will know the size (mode) and direction of the resultant force. In fact, it will be clearer to have CAD drawing software here, because not only the component vectors of each vector can be drawn, but also the model can be directly established in the spatial rectangular coordinate system, making each vector more intuitive, clearer and easier to analyze. The above picture is for reference and explanation only.