i need help on these questions please help and please give me full explanation. thank you

3. Determine whether the sequence with the given n\" term is monotonic. Discuss the boundedness of the sequence. n _ cosn 2... (b) an ~ n 4. Find the radius and the interval of convergence of the power series. on n+1 r: on n (a) 2(4) (xS) 2(33') (3) an = b . n5" ( ) 0 (2n)! 5. Find the intervals of convergence for f , f :1 f . M" (x _1)n+l n+1 (a) f (x) =iH) 2 x24 6. Find a power series for f(x) = centered at 0 and nd the interval for convergence