The sum to infinity of a G.P. is 16 and the sum of the first 4terms is 15. Find the first 4 terms.

Find the sum to infinity of the following (if they converge).
?(a)4+4/3+4/3²+...
(b)9+7+5+3+...(can't do, its an AP ?)
(c)20-10+5-2.5+...a=20,r=-0.5
?(d)5/10+5/100+5/1000+...
(e)p+p²+p³+...a=p,r=p
?(f)3-1+1/3-1/9+...

S(infinity)=1/(a-r)

does b converge?

d. Denke, in decimals. 0.555555555555...