Question

find 20th term of AP 15 12 9 6

Answer 1

♠ ANSWER :

❇ Given,, A. P. = 15, 12, 9, 6.

First term, a = 15

Common difference, d = a2 - a1 = 12 - 15 = - 3

20th term, A20 = a + ( n - 1 ) d

A20 = 15 + ( 20 - 1 ) ( - 3 )

A20 = 15 + 19 ( - 3 )

A20 = 15 - 57

A20 = - 42.

Answer 2

$\huge \mathbb{Hello \: Friends}$

$\boxed{ \red Ans = = > > \: }$

$\blue{Given \: AP :}$

$\bf{15 ,\: \: \: 12, \: \: \: 9, \: \: \: 6 ,\: .....}$

$\bf{Here : }$

T₁ = 15 , T₂ = 12, T₃ = 9 , T₄ = 6

a = T₁

$\bf{a \: = 15}$

d = T₂ - T₁

d = 12 - 15

d = -3

$\bf{d \: = - 3}$

$\bf {To \: find : }$

T₂₀ = ??

∴ n = 20

$\pink{We \: know \: that..}$

$\bf{tn \: = a \: + (n - 1)d} \\ \\ \bf{t20 = 15 + (20 - 1) \times - 3}$

$\bf{ = 15 + 19 \times - 3}$

$\bf{ = 15 - 57}$

$\bf{ = - 42}$

$\huge \boxed{T20= - 42}$

$\huge \frak{Thanks}$