Three numbers form a geometric sequence. Their sum is 21 and their product is 64. Find the numbers(please show working)

Question

anonymous · Answer

a,b,c$$S_n=\frac{ a(1-r^n) }{ 1-r }$$
$$\frac{ T_2 }{ T_1 }=\frac{ T_3 }{ T_2 }$$

anonymous · Answer

So from here how do I continue this is what I've tried so far and it's not getting me anywhere:
(T2/T1)=(b/a)r and (T3/T2)=(c/b)r

anonymous · Answer

b/a=c/b
b^2=ac

anonymous · Answer

so we have$$a+b+c=21$$
$$abc=64$$
$$b^2=ac$$
3 equations 3 unknowns ,solve

hartnn · Answer

u can easily find b from 
abc=64 and b^2=ac

hartnn · Answer

try it, if u can't i'll help u

anonymous · Answer

k, an trying this out now
already got b=4

hartnn · Answer

thats correct, now u know how u can get a,c ?

anonymous · Answer

just got it, a=1,b=4,c=16 thanks alot!