A Level Maths Notes: C4 – The Product of Two Binomial Expansions
The General Binomial Expansion takes the form
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Any expression of the
form
can
be evaluated using this expression whatever the values of A and B –
negative, decimal factional or even complex numbers.
We can expand the product of two binomial expansions by finding each individual binomial expansion.
Example: Expand
up
to and including the term in![]()
We expand each expression up
to
![]()

Simplifying the constant for each term gives
![]()
![]()
Simplifying the constant for each term gives
![]()
Now we multiply the binomial expansions together:
![]()
![]()
Each term in brackets can then be simplified.
The first expansion is only
valid for
and
the second is only valid for
so
the product is only valid for the smallest of these two intervals:![]()