Question

Find the common difference of an AP whose An: -3n+7

Answer 1

Given :

an=3n+7......(1)

Put n=1 in equation 1

a1=3×1+7

a1=3+7

a1=10

Put n=2 in equation 1

a2=3×2+7

a2=6+7

a2=13

Put n=3 in equation 1

a3=3×3+7

a3=9+7

a3=16

First three terms of an AP

are = 10 , 13 , 16

Common difference (d)=

a2-a1 or a3-a2

d=a2-a1 = 13-10

d= 3

Hence , the common difference

of an AP is 3

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