Task 3 is also easy:
(define (task-3 a b)
(+ (* (+ 333 3/4) (expt b 6))
(* (expt a 2) (- (* 11 (expt a 2) (expt b 2))
(expt b 6)
(* 121 (expt b 4))
2))
(* (+ 5 1/2) (expt b 8))
(/ a (* 2 b))))
(display "Task 3:\n")
(let ((result (task-3 77617 33096)))
(display `(,result (approx: ,(exact->inexact result)))))
(newline)>>3
Irrational numbers have an infinite number of non-repeating decimals, the only exact way to represent them is symbolic:
(define (task-2 years)
(let loop ((n 1) (e 1) (m 1))
(if (<= n years)
(loop (+ n 1) (* e n) (+ (* m n) 1))
`(- (* ,e e) ,m))))
(display "Task 2:\n")
(display (task-2 25))
(newline)