Question

WHAT is the common difference of an ap in which a21-a7=84 class 10​

Answer 1

Hey mate

Here is your answer

a21-a7=84

a+20d-a-6d=84

14d=84

d=6

Common difference of AP is 6.

Hope it helps you

Answer 2

$\large{\implies{Answer}}$

$a21 - a7 = 84 \\ a + (21 - 1)d - (a + (7 - 1)d = 84 \\ a + 20d - (a + 6d) = 84 \\ a + 20d - a - 6d = 84 \\ 20d - 6d = 84 \\ 14d = 84 \\ d = \frac{84}{14}$

$\large{\implies{d=6}}$