Question

1.Find the first terms and common difference of the Arithmetic Progression whose nth term is tn=-3+2n.

2.Find the sum of

(1) 1+3+5+......40terms.
(2)1+3+5+......+55​

Answer 1

Step-by-step explanation:

$2. \: \: \: a = 1 \\ n = 40 \\ d = a2 - a1 = 3 - 1 = 2 \\ sum = \frac{n}{2} (2a + ( n- 1)d) \\ = \frac{40}{2} (2 \times 1 + (40 - 1)2 \\ = 20(2 + 39 \times 2) \\ = 20(2 + 78)$20*80=1600