C2 DOUBT edexcel

[halosh92]

(a) Expand (2 + y)^6 in ascending powers of y as far as the term in y^3, simplifying
each coefficient.
(b) Hence expand (2 + x ? x^2)^6 in ascending powers of x as far as the term in x^3,
simplifying each coefficient.

i know how to do the (a) part but am stuck at part (b)

[astarmathsandphysics]

Can you restate the question?

[halosh92]

Can you restate the question?

how do u do the second part?

[astarmathsandphysics]

I meant this (2 + x ? x^2)^6
with the question mark in the middle

[halosh92]

I meant this (2 + x ? x^2)^6
with the question mark in the middle

sorry typing mistake its:
(2+ x- x^2)^6

[astarmathsandphysics]

Ok will do it when I get home

[astarmathsandphysics]

(2+x)^6=1*2^6*x^0+6*2^5*x^1+15*2^4*x^2+20*2^3*x^3+....
=64+192x+240x^2+160x^3....
Now replace all the x's by x-x^2
64+192(x-x^2)+240(x-x^2)^2 +160(x-x^2)^3
64-192x-192x^2+240(x^2-2x^3)+160x^3 ignoring all powers of x higher than x^3
=64+192x+48x^2-320x^3

[halosh92]

(2+x)^6=1*2^6*x^0+6*2^5*x^1+15*2^4*x^2+20*2^3*x^3+....
=64+192x+240x^2+160x^3....
Now replace all the x's by x-x^2
64+192(x-x^2)+240(x-x^2)^2 +160(x-x^2)^3
64-192x-192x^2+240(x^2-2x^3)+160x^3 ignoring all powers of x higher than x^3
=64+192x+48x^2-320x^3

ok thankyou!!!!