Given k is a real positive number, the third term of the expansion of (-2x +k)^12 ordered according to the decrease of x exponents is 66x^10. What's the value of k?

a) 1/64
b) 1/32
c) 1/66
d) 1/58

Binomial again... Pls help!

Question

Given k is a real positive number, the third term of the expansion of (-2x +k)^12 ordered according to the decrease of x exponents is 66x^10. What's the value of k?

a) 1/64 
b) 1/32 
c) 1/66 
d) 1/58

Binomial again... Pls help!

anonymous · Answer

@KingGeorge Could you help me again pls King?

anonymous · Answer

1/32

anonymous · Answer

Nevermind, I got it. I wanted to calculate the term 66x^10 but I found it on wolfram. Its 67584k²x^10. So I did 66x^10 = 67584k²x^10 and got 1/32. Option B.
I just need to know how to calculate a determined term without having to go through the whole process. I need to learn the formula by heart, right?

anonymous · Answer

Oh, thanks cinar!

kinggeorge · Answer

@MelindaR Sorry I was gone. I had to go figure out how to do my own math homework. 

Learning the formula by heart is definitely the best way to go about it. Once you know the formula, you can calculate whatever term you need and solve for whatever variable you need to.

anonymous · Answer

Np. Haha, funny.
Mmm I see. I will just keep practicing, then. Thanks!

kinggeorge · Answer

You're welcome. Feel free to ask any more questions.