GEOMETRICAL PROGRESSION A3

 

Find the sum of the 1st eight terms of the geometrical progression 4+16+64+…….

 

Solution

 

G₁ = 4, r=4, n=8

 

S_n = G₁(rⁿ-1)/ r-1

             

 

S₈ = 4(4⁸-1)/4-1

             

 

S₈ = 4(4⁸-1)/3 

             

 

S₈ = 4(262144-1)

             3

 

S₈ = 4(262,143)

             3

 

 

S₈ = 349,524

            

 

 

Hence the sum of the 1st eight terms is 349,524.

 

TRY THIS……………..

 

 

Find the sum of the 1st eight terms of the geometrical progression 3+12+48+…….