Binomial confusion... help (1 Viewer)

[darkphoenix]

ok, so this is the question: to find the independent term of x where (x+(1/x))^40)(x-(1/x))^40)

when I didn't factorise this and working with the first bracket and then times the second bracket , it's this 40C20 * 40C20
yet if i factorise it into (x^2- x^(-2)) the answer is 40C20. Wth... can someone explain why this is happening?

 

[funnytomato]

ok, so this is the question: to find the independent term of x where (x+(1/x))^40)(x-(1/x))^40)

when I didn't factorise this and working with the first bracket and then times the second bracket , it's this 40C20 * 40C20yet if i factorise it into (x^2- x^(-2)) the answer is 40C20. Wth... can someone explain why this is happening?

you should probably check your working for that step

 

[darkphoenix]

your right, i missed about bunch of other negative independent terms... thanks I got it now