What is the common difference of an AP in which a21-a7 84?2

1.	What is the common difference of an AP in which a21-a7 84?2
Answer» Let common difference be d and first term be a So, given a(21) - a(7) = 84 a + 20d - ( a + 6d ) = 84 20d - 6d = 84 14d = 84 d = 6 For AP nth terman = a1 + (n-1)d Then, a21 = a1 + 20da7 = a1 + 6d Given, a11 - a7 = 84(a1 + 20d) - (a1 + 6d) = 8414d = 84d = 84/14 = 6 Common difference = 6

Answer»

Let common difference be d and first term be a So, given

a(21) - a(7) = 84

a + 20d - ( a + 6d ) = 84

20d - 6d = 84

14d = 84

d = 6

For AP nth terman = a1 + (n-1)d

Then, a21 = a1 + 20da7 = a1 + 6d

Given, a11 - a7 = 84(a1 + 20d) - (a1 + 6d) = 8414d = 84d = 84/14 = 6

Common difference = 6

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