2 easy question

1)A : (A+B) : (A+B+C) = 1³ : (1+2)³ : (1+2+3)³
A : (A+B) : (A+B+C) = 1 : 27 : 216
A : (A+B - A) : (A+B+C - A - B) = 1 : (27 - 1) : (216 - 1 - 27)
A : B : C = 1 : 26 : 188
2)1st term a = - 1 , common ratio r = - 1/x ,
and |r| = |- 1/x| < 1 since x > 1.Sum to infinity of G.S. with |r| < 1
= a / (1 - r)
= - 1 / (1 - (-1/x))
= - 1 / (1 + 1/x)
= - x / (x+1)

2012-07-27 20:21:49 補充：
Correction for 1) :

A : (A+B - A) : (A+B+C - A - B) = 1 : (27 - 1) : (216 - 27)
A : B : C = 1 : 26 : 189

Sorry of my mistakes~