a = -6
ar^4 = 48
divide, and you have r^4 = -8
Now, that's impossible, since all even powers are positive. Maybe you meant that the 4th term is 48. In that case r^3 = -8 and r = -2
So S4 = a(r^4-1)/(a-1) = -6(2^4-1)/(-2-1) = -6*15/-3 = 30
The sequence is -6, 12, -24, 48, ...
if the first and fifth term of a GP is -6 and 48 respectively find the sum first four terms
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