The bending produced by each weight will also be represented precisely like that in Fig. 12. The triangle _ANB_ represents the bending produced by _W_₁; _AOB_ the bending produced by _W_₂; and _APB_ the bending produced by _W_₃. The resultant bending effect produced by the three loads or weights acting simultaneously is simply the summation of the three effects each due to a single load. Hence _DC_ is erected vertically through the point of application of _W_₁, so as to equal _DN_ added to the two vertical intercepts between _AB_ and _AP_, and _AB_ and _AO_. Similarly, _HF_ is equal to _HO_ added to the intercepts between _AB_ and _AP_, and _AB_ and _BN_. Finally, _KL_ is equal to _PL_ added to the other two intercepts, one between _AB_ and _BN_, and the other between _AB_ and _BO_. Straight lines then are drawn through _A_, _C_, _F_, _K_, and _B_. Any vertical intercept between _AB_ and _ACFKB_ will represent the bending moment in the beam at the corresponding point. Obviously any number of loads of any magnitude, or a uniform load, may be treated in precisely the same way. An important practical rule can readily be deduced from the equations (16), each one of which may be regarded as a general equation of moments. If the system of three, or any other number of loads, be moved a small distance Δ_x_, while they all remain separated by the same distances as before, the bending moment _M_ will be changed by the amount shown in equation (16_a_): _ΔM = RΔx - W₁Δx - W₂Δx -_ etc. (16_a_) If the notation of the differential calculus be used by writing the letter _d_ instead of Δ, and if both members of equation (16_a_) be then divided by _dx_, equation (16_b_) will result: _ΔM dM_ --- = ---- = _R - W₁ - W₂_ - etc. = shear. (16_b_) _Δx dx_