Question

1) find 25the term of A.P. 7 ,12 ,17……..

2).find the sum of first 12 terms of A.P. 4 , 7 , 10……​

Answer 1

Answer:

1) 127

2) 246

Step-by-step explanation:

1) a = 7, d = 5

an = a + (n-1)d

a25 = 7 + 24×5

= 7+ 120 = 127

2) a = 4, d = 3

Sn = n/2[2a + (n-1)d]

S12 = 12/2 × (8 + 11×3)

= 6 × 41 = 246

Answer 2

Step-by-step explanation:

1)

a25 = a+24d

=7+24(5)

= 7+ 120

= 127

2)

S12 = n/2[2a+(n-1)d]

=12/2[2(4) + 11(3)]

= 6(8+33)

= 6(41)

= 246

Hope it helps.