Answers
Answer:
5th term
Step-by-step explanation:
Given: GP = 2, 8, 32, ... 512
To Find: Which term is 512
General Form of a Term in GP = arⁿ⁻¹
Here 'n' refers to the cardinal value of the term. ( Like 1st, 2nd, 3rd, etc. )
⇒ arⁿ⁻¹ = 512
According to the GP,
a = 2, r = 4
Substituting the values we get,
⇒ 2 × 4ⁿ⁻¹ = 512
⇒ 4ⁿ⁻¹ = 512 / 2 = 256
256 can also be written as 4⁴
⇒ 4ⁿ⁻¹ = 4⁴
Since Bases are equal, we can equate the powers. Hence we get,
⇒ n - 1 = 4
⇒ n = 4 + 1
⇒ n = 5
Hence 512 is the 5th term of the GP.
⇒ given G.P. : 2, 8, 32, .........is 512
a = 2 ; r = a₂ / a₁ = 8 / 2 = 4
let nth term of the G.P. be 512
an = a . r ⁿ⁻¹
512 =2 × (4)ⁿ⁻¹
2⁹ = 2 × (2²) ⁿ⁻¹ [512 can be written as 2⁹]
2⁹ = 2¹ 2²⁽ⁿ⁻¹⁾
2⁹ = 2²ⁿ⁻²⁺¹
2⁹ = 2²ⁿ⁻¹
512 = 2⁹
2n-1 = 9 [bases are equal, exponents are also equal]
2n = 9+1
n= 10/2 = 5
Hence , 512 is the 5th term of the given G.P.