(5r5 – 3s3)(-25r10 – 15r5s3 – 9s6) = -125r15 - 75r10s3 - 45r5s6 + 75r10s3 + 45r5s6 + 27s9 = -125r15 + 27s9
Ответ: -125r15 + 27s9