Question:

if 1+y, 1+3y, 1+4y (y cant be 0..sorry i dont know how to write it in math equation here ) are three consecutive terms of a Geometric Progression. Find

(a) the value of y

(b) the sum to infinity.

the ans from book

(a) -1/5

(b) 8/5

but i have calculate and get this ans

(a) 1/5

(b) -18/5

thank for your advice