which is a root with has algebraic multiplicity of >1. for root with multiplicity of 𝑚 (∑𝑚𝑖=0𝐶𝑖𝑡𝑖)𝑒𝑟𝑡 for example (𝐶1𝑡+𝐶2)𝑒𝑟𝑡 if multiplicity of 2.