What is the common difference of an A.P. in which a21 - a7 = 84?

Q1 of 47 Page 1

What is the common difference of an A.P. in which a₂₁ - a₇ = 84?

Let the common difference be 'd' and first term be 'a'.

And we know that, nth term of an AP is

a_n =a + (n - 1)d

Given, a₂₁ - a₇ = 84

⇒ a + 20d - (a + 6d) = 84

⇒ 14d = 84

⇒ d = 6

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