Question & Answer

Find the common difference if ${n^{th}}$ term of an A.P. is 2n + 1.

ANSWER Verified Verified
Hint- In this particular type of question we have to use the given relation between the ${n^{th}}$ term and n to find any two successive terms of the AP. Then we need to subtract them to find the desired common difference.

Complete step-by-step answer:
${n^{th}}$ term= 2n+1
1st term ( putting n = 1 ) = $2 \times 1 + 1 = 3$
2nd term ( putting n = 2 ) = $2 \times 2 + 1 = 5$
Common difference is difference of two successive terms of AP ( Second term - First term).
 d = 5-3 = 2

Note- Remember to recall the concept of common difference of an AP to solve such questions. Note that in this question the formula for ${n^{th}}$ term of an AP is not required as a direct relation between the ${n^{th}}$ term and n is given. The common difference could also be calculated by using any two successive terms other than 1 and 2.