Hi guys, just come across something in the Core Mathematics 2 textbook that I'm a bit stuck on (page 84, q6) <-- just incase I write it out horribly
I've managed to solve this question with a little nudge in the right direction but I was wondering if there was a different, slightly quicker method to solving it. Here's the question;
The coefficient of
x2 in the binomial expansion of
(1+2x)n, where n is a positive integer, is 7. Find the value of n.
Okay, so I figured that the coefficient of
x2, which is 7, is equal to
4n. From that I get 28, and that's where I got stuck. Someone told me that I know the answer is 8 because 28 is in the expansion of
(a+b)8, but surely there's a quicker way than sitting there writing out pascal's triangle all the way to 8?!
Any help is greatly appreciated as usual :P