SEQUENCE AND SERIES A8

Find the sum of the 1st eight terms of the geometrical progression 2+4+8+16+…….

solution

G₁ = 2, r=2, n=8

S_n = G₁(rⁿ-1)/r-1

               

S₈ = 2(2⁸-1)/2-1

             

S₈ = 2(2⁸-1)/1

              

S₈ = 2(2⁸-1)

S₈ = 2(256-1)

S₈ = 2(255)

S₈ = 510

Hence the sum of the 1st eight terms is 510.