How do use the binomial theorem to calculate 10C7?

1 Answer
Aug 15, 2017

120120

Explanation:

"using the definition of the "color(blue)"binomial coefficient"using the definition of the binomial coefficient

color(white)(x)^nC_r=(n!)/(r!(n-r)!)xnCr=n!r!(nr)!

"where "n! =n(n-1)(n-2)......xx1

rArr^(10)C_7=(10!)/(7!xx3!)

color(white)(xxxxxx)=(10xx9xx8xxcolor(red)cancel(7xx6xx5xx4xx3xx2))/(color(red)cancel(7xx6xx5xx4xx3xx2)xx3xx2

color(white)(xxxxxx)=(10xx9xx8)/(3xx2)=120