SOLUTION: How do I cube (3 minus square root of 7)?

Algebra ->  Square-cubic-other-roots -> SOLUTION: How do I cube (3 minus square root of 7)?      Log On


   

Question 394734: How do I cube (3 minus square root of 7)?
Found 2 solutions by MCAT, jrfrunner:
Answer by MCAT(6) About Me  (Show Source):
You can put this solution on YOUR website!
√7=2.65, 2.65-3=-0.35, -0.35^3=-0.04

Answer by jrfrunner(365) About Me  (Show Source):
You can put this solution on YOUR website!
use the binomial expansion %28a%2Bb%29%5En = (Cn,n)*a%5En+(Cn,1)a%5E%28n-1%29b+...(Cn,0)*b%5En
where Cnx= combinations= n!/[x!*(n-x)!] and comes from pascal triangle. Are you familiar with that?
-
in your case
a=3
b=-sqrt%287%29
n=3

%283-sqrt%287%29%29%5E3+=+27+-27%2Asqrt%287%29%2B63-7sqrt%287%29%29
%283-sqrt%287%29%29%5E3+=+90+-34%2Asqrt%287%29