Find the indicated sum Use the formula for the sum of the fi

Find the indicated sum. Use the formula for the sum of the first n terms of a geometric sequence.^8 sigma _i = 1 4^i

Solution

The above expression can be written as

4 +4²+4³+4⁴+......+4⁸

This is in geometric progression

where a₁=4

common ratio r=4

S_n=a₁(rⁿ-1)/(r-1) = 4(4⁸-1)/3

S_n= 4* 65535/3= 4*21845=87380