Answer:
R₂ = V₂R₁/(E + V₂)
Step-by-step explanation:
By voltage divider, V₂ = ER₂/(R₁ + R₂)
So, cross-multiplying, we have
V₂(R₁ + R₂) = ER₂
expanding the bracket, we have
V₂R₁ + V₂R₂ = ER₂
collecting like terms, we have
V₂R₁ = ER₂ + V₂R₂
factorizing, we have
V₂R₁ = (E + V₂)R₂
dividing through by (E + V₂), we have
R₂ = V₂R₁/(E + V₂)