Question

if a =20 ,d= -2 find t21​

Answer 1

Answer:

Given:

a = 20 , d = -2  ,  n = 21

To Find:

t21

Proof:

tn = a + [n-1] d

t21 = 20 + [20] [-2]

t21 = 20-40

t21 = -20

Answer 2

$a = 20 \\ d = - 2 \\ \\ \pink{ \large{tn = a + (n - 1)d}} \\ \\ t21 = 20 + (21 -1 ) \times ( - 2) \\ \\ t21 = 20 + 20 \times ( - 2) \\ \\ t21 = 20 - 40 \\ \\ \blue{ t21 = - 20}$