Binomial Theorem 3

[IloveManUtd]

Find, in ascending powers of x, the first three terms of (1+kx)[sup:262hd7sh]4[/sup:262hd7sh](1-4x)[sup:262hd7sh]3[/sup:262hd7sh].

I've found the first 3 terms of each:
(1+kx)[sup:262hd7sh]4[/sup:262hd7sh] = 1 + 4kx + 6k[sup:262hd7sh]2[/sup:262hd7sh]x[sup:262hd7sh]2[/sup:262hd7sh] and
(1-4x)[sup:262hd7sh]3[/sup:262hd7sh] = 1 - 12x + 48x[sup:262hd7sh]2[/sup:262hd7sh]

How do I multiply them to get the answer. PLEASE HELP

 

[tkhunny]

You multiple them. How else? I am almost certain you learned multiplication in elementary school. Do that.

1 * 1 = 1
1 * 4kx = 4kx
1 * 6 k^2 x^2 = 6 k^2 x^2
-12x * 1 = -12x
-12x * 4kx = -48k x^2
etc...

Are you SURE that using the first three terms of each factor that you will get the first three terms of the product? You had better prove it.