Can use it to quickly expand (x + 2y) cubed and can also use it to find specific coefficient of for example x squared in (1+x)^7
1 of 6
factorial and n choose r
n choose r = n! / r! (n-r)!
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Pascals triangle and n choose r
if looking to find nth entry in r row of triangle do r-1 choose n-1
3 of 6
expansion of bracket with 1 e.g. (1 +y) cubed
ignore one and do ncr and increase y by one power each time
first term if just nc0 (no y term)
4 of 6
Tip
Remember ...
5 of 6
expansion of bracket when a is more than 1 e.g. (2 + z) cubed
do first term (2) to the power of power of bracket
Then + 4 choose 1 first term to the power of bracket - 1 multiplied by second term (z) to power of 1
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