Show, by substituting them into the recurrence relation, that x n = 2 n and x n

Question:

Show, by substituting them into the recurrence relation, that x_n = 2ⁿ and x_n = (–1)n are two solutions of x_{n + 2} – x_{n + 1} – 2x_n = 0. Verify similarly that x_n = A(2ⁿ) + B(–1)ⁿ is also a solution of the recurrence relation for all constants A and B.