Use the summation formulas to rewrite the expression without the summation notation Use the result to find the sums for n 10 100 1000 and 10 000 Step 1 IM i 1 Using the summation formula the expression Step 2 summation notation Therefore 6i 2 n i 1 6i 2 n 3 S 3 0005 Therefore S n 3 S Now to find the sums for 5 S n 3 n i 1 1 5 n W i 1 6i 2 6i 2 n 6i n i 1 can be 6 n n 1 2 2n can be written as the expression without the 2n 10 100 1000 and 10 000 substitute the value of in