What is the common difference of the arithmetic sequence. 25, 18, 11, 4,?

Jul 20, 2016

$d = - 7$

Explanation:

The common difference is found by subtracting any two consecutive terms in an AP.

$d = {T}_{4} - {T}_{3} \text{ "=" " T_3 - T_2" " = " } {T}_{2} - {T}_{1}$

If you get the same answer, you know it is an AP.

If $d$, is positive, then the terms get bigger.

If $d$, is negative, then the terms get smaller.

In this case

$d = {T}_{4} - {T}_{3} \text{ "=" } 4 - 11 = - 7$

${T}_{3} - {T}_{2} \text{ " = " } 11 - 18 = - 7$

${T}_{2} - {T}_{1} \text{ "= " } 18 - 25 = - 7$