Hello everyone.(adsbygoogle = window.adsbygoogle || []).push({});

I'm studying for my exam and i'm reveiwing some problems but this one isn't making sense to me:

11^9(9 choose 0) - 11^8(9 choose 1) + 11^7(9 choose 2) - .... - 11^2(9 choose 7) + 11^1 (9 choose 8) - 11^0 (9 choose 9)

answer:

(11-1)^9 = 10^9 = 1,000,000,000.

work looked like:

(9 choose 0) 11^9 (-1)^0 + (9 choose 1)11^8(-1)^1

Can someone explain to me how they did this?

I see the 11 is decreasing, and the signs are alternating, it looks like a binomial expansion but i'm not seeing how they simplified that.

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Is this a geometric progression? or binomial expansion i'm not sure how they got 10^9

**Physics Forums | Science Articles, Homework Help, Discussion**