Binomial Expansion Help | Mathematics | Page 1

lean hedge Jun 28, 2025, 7:33 AM

#

Im really struggling with question 7D. I understand how to apply the formula but I'm not sure how to continue to find r. The working shows that r=2 but I don't understand how to get here. Any help is much appreciated thank you 🙂

livid hedgeBOT Jun 28, 2025, 7:33 AM

#

clear perch Jun 28, 2025, 9:17 AM

#

@lean hedge You have a^{13-r} * a^{-r} = a^{13-2r}

#

13 - 2r = 9

lean hedge Jun 28, 2025, 9:42 AM

#

ahhh

#

thank you so much

#

i finally clicked

#

thanks!

#

.close

#Binomial Expansion Help