Разложение многочленов

(define (factorize l)
  (if (equal? (car l) '-)
      (let ((a (cadr l)) (b (caddr l)))
           (if (= (caddr a) 2)
               (list '* (list '- (cadr a) (cadr b))
                        (list '+ (cadr a) (cadr b)))
               (list '* (list '- (cadr a) (cadr b))
                        (list '+ (list 'expt (cadr a) 2)
                                 (list '* (cadr a) (cadr b))
                                 (list 'expt (cadr b) 2)))))
      (let ((a (cadr l)) (b (caddr l)))
        (list '* (list '+ (cadr a) (cadr b))
                 (list '+ (list 'expt (cadr a) 2)
                          (list '- (list '* (cadr a) (cadr b)))
                          (list 'expt (cadr b) 2))))))