Ive done this (I think) and got:Find the coefficiant of in the expansion of
I cannot find a coeficciant of because, after expanding the 2 brackets. Upon multiplying them both together, the 2 's that are in each bracket make an therefore eradicating a coefficiant of
Any help would be greatly appreciated as if this comes up in the exam, I would be prety stuck
Higher powers of x will not be involved in computing the term, since multiplications of those will only contribute to higher powers of x.
The x term results from the multiplication of x by the constant.
The resultant x term is the sum of the constant from one factor multiplied by the x term in the other factor from both sets of factors.
When CaptainBlack wrote out the pair of square brackets multiplied together,
he only wrote out the first few terms of the binomial expansions, as higher powers of x will not contribute to the term.
That's all the question wanted you to discover.
The question wanted you to see that only a pair of terms from both expansions contribute to the resultant x term.
CaptainBlack placed the first few terms of the binomial expansions of both and into the square brackets, as it is unnecessary to write the rest of them to obtain the coefficient of the term only.
if you needed the entire expansion, then all the terms of both would be required.