The reaction forces at support A and B are Ra = 21.67 kN and Rb = 21.67 kN, respectively. The expression for the reaction forces can be obtained by taking the moment about any of the supports and equating it to zero.
Given information: A uniform dead load of 10 kN/m. A single live concentrated force of 25 kN. The expression for the reaction forces of the beam is obtained by taking the moment about any of the supports and equating it to zero.Let's consider the moment about the left support A:ΣMₐ = 0(10 × 4) + (25 × 2) - Rₐ × 6 = 0. Here, Rₐ is the reaction force at support A. Ra = (80 + 50)/6Rₐ = 21.67 kN. As the beam is symmetrical about the center, the vertical reaction force at the right support, Rb, is equal to Rₐ.Rb = Rₐ = 21.67 kN.