hi guys... this is my first thread in this forum.. i hope i'll learn math more easily with this forum... mmm.. i've a some math homework that i must submit it this Thursday... :tongue2: but, i don't know how to answer it... the questions is... 1. Prove that X ⊆ X U Y for all sets X and Y... 2. A sequence r is defined as rn = 3.2ⁿ - 4.5ⁿ, n≥0. Prove that the sequence satisfied rn = 7rn-1 - 10rn-2, n≥2. anyone have the solution for these question???