Question

Let the sum of n 2n 3n term of ap be S1 S2 S3 respectively.show that S3=3(S2-S1)

Answer 1

Answer:

Step-by-step explanation:

Let ‘a’ be the first term of the AP and ‘d’ be the common difference S1 = (n/2)[2a + (n – 1)d] --- (1)

S2 = (2n/2)[2a + (2n – 1)d]

= n[2a + (n – 1)d] --- (2)

S3 = (3n/2)[2a + (3n – 1)d] --- (3)

Consider the RHS: 3(S2 – S1) = S3

= L.H.S ∴ S3 = 3(S2 - S1) .

Answer 2

plz refer to this attachment