The sum of first n, 2n and 3n terms of an A.P. are `S_(1), S_(2), S_(3)` respectively. Prove that `S_(3)=3(S_(2)-S_(1))`.

Let sum of n , 2n , 3n , terms of an A.P are S_(1), S_(2), S_(3) respectively. Prove that S_(3) = 3 (S_(2) - S_(1)) .

First term and common difference of an A.P. are 6 and 3 respectively : Find S_27

Let S_n denote the sum of first n terms of an A.P. If S_(2n)=3S_n , then find the ratio S_(3n)//S_ndot

If S_1, S_2, S_3 are the sum of first n natural numbers, their squares and their cubes, respectively , show that 9 S_(2)^(2) = S_(3) (1+ 8S_1)

Let each of the circles S_(1)-=x^(2)+y^(2)+4y-1=0 S_(1)-= x^(2)+y^(2)+6x+y+8=0 S_(3)-=x^(2)+y^(2)-4x-4y-37=0 touch the other two. Also, let P_(1),P_(2) and P_(3) be the points of contact of S_(1) and S_(2) , S_(2) and S_(3) , and S_(3) , respectively, C_(1),C_(2) and C_(3) are the centres of S_(1),S_(2) and S_(3) respectively. The ratio ("area"(DeltaP_(1)P_(2)P_(3)))/("area"(DeltaC_(1)C_(2)C_(3))) is equal to

Let s_(n) denote the sum of first n terms of an A.P. and S_(2n) = 3S_(n) . If S_(3n) = kS_(n) then the value of k is equal to

Let each of the circles S_(1)-=x^(2)+y^(2)+4y-1=0 S_(1)-= x^(2)+y^(2)+6x+y+8=0 S_(3)-=x^(2)+y^(2)-4x-4y-37=0 touch the other two. Also, let P_(1),P_(2) and P_(3) be the points of contact of S_(1) and S_(2) , S_(2) and S_(3) , and S_(3) , respectively, C_(1),C_(2) and C_(3) are the centres of S_(1),S_(2) and S_(3) respectively. P_(2) and P_(3) are images of each other with respect to the line

If S_(n) denotes the sum of n terms of an A.P., S_(n +3) - 3S_(n + 2) + 3S_(n + 1) - S_(n) =