Welcome to NRICH.

 
Expanding (1 + x + 3x2)5
By Hal 2001 (P3046) on Saturday, November 25, 2000 - 01:09 pm:

I have forgotton how to go about expanding the following. Can anyone refresh my memory for me?

a) (1 + x + 3x2)5, say up to x3 term.
b) also in the general case, (1 + x + x2)n
c) (x - (1/x))n

Thanks.
~Hal

By Anonymous on Saturday, November 25, 2000 - 04:43 pm:

Hey HAL,

for (a) just group (1+x) together and use the binomial expansion for 2 terms!

By Hal 2001 (P3046) on Saturday, November 25, 2000 - 07:30 pm:

Right, I'll give that a go!