(define (+terme L1 L2)
  (cond ((leere-termliste? L1) L2)
        ((leere-termliste? L2) L1)
        (else
         (let ((t1 (erster-term L1))
               (t2 (erster-term L2)))
           (cond
             ((> (grad t1) (grad t2))
                (term-anhaengen t1
                    (+terme (rest-terme L1) L2)))
             ((< (grad t1) (grad t2))
                (term-anhaengen t2
                    (+terme L1 (rest-terme L2))))
             (else
               (term-anhaengen
                  (konstr-term (grad t1)
                               (add (koeff t1)
                                    (koeff t2)))
                  (+terme (rest-terme L1)
                          (rest-terme L2)))))))))


(define (*terme L1 L2)
  (if (leere-termliste? L1)
      (leere-termliste)
      (+terme (*-term-mit-allen-termen
                        (erster-term L1) L2)
              (*terme (rest-terme L1) L2))))

(define (*-term-mit-allen-termen t1 L)
  (if (leere-termliste? L)
      (leere-termliste)
      (let ((t2 (erster-term L)))
        (term-anhaengen
               (konstr-term (+ (grad t1)
                               (grad t2))
                            (mul (koeff t1)
                                 (koeff t2)))
               (*-term-mit-allen-termen
                          t1 (rest-terme L))))))