#
The sum of the first 10 terns of an arithmetic sequence is 530.What is the first term if the last term is 80? What is the common difference? with solution

1
by viv1

Log in to add a comment

by viv1

Log in to add a comment

or use the formula: Sum of the terms= n/2 (2 a sub 1 + (n-1)d) or Sum of the terms= n/2 (a sub 1 + a sub n)

use the second sum formula..

530=10/2 (a sub 1 + 80)

530= 5 (a sub 1 + 80)

530= 5(a sub 1) + 400

530-400= 5(a sub 1)

130= 5 (a sub 1)

130/5= a sub 1

26= a sub 1

the first term is 26. now u have the first term...

use the first arithmetic formula...

80= 26+(10-1)d

80= 26 + 9d

80-26= 9d

54= 9d

54/9=d

6=d

the common difference is 6...

those are the answers...