Answer
True
Work Step by Step
If $\lambda$ is an eigenvalue of the matrix A,
obtain $A^3v=A^2(Av)=A^2(\lambda v)=\lambda (A^2v)=\lambda (\lambda^2 v)=\lambda^3 v$
Hence, If $\lambda$ is an eigenvalue of the matrix A, then $\lambda^3$ is an eigenvalue of A^3.