Chapter 10 Counting Methods and Probability - 10.2 Use Combinations and Binomial Theorem - 10.2 Exercises - Skill Practice - Page 695: 23

$$128s^7-448s^6t^4+672s^5t^8-560s^4t^{12}+280s^3t^{16}-84s^2t^{20}+14st^{24}-t^{28}$$

We know from the Binomial Theorem (page 693) that we can expand the given expression without multiplying it out. Doing this, we obtain: $$128s^7-448s^6t^4+672s^5t^8-560s^4t^{12}+280s^3t^{16}-84s^2t^{20}+14st^{24}-t^{28}$$