Question

First term and common difference of an A.P. are 1 and 2 respectively ; find: a = 1, d = 2,S75=?,Sn =n/2 [□ + (n – 1)d]. S75= 75/2[2+ (75 – 1) □] ,S75= 75/2× □,S75 = 75/2× 150 = □ ,S75= ………..



plzz answer fast ​

Answer 1

Answer:

$S_{75} = 5625$

Step-by-step explanation:

First term (a) = 1

Common Difference (d) = 2

n = 75

$S_{75} = \frac{n}{2} (2a+(n-1)d)\\\\ = \frac{75}{2}(2(1)+(75-1)2) \\\\= \frac{75}{2} (2+148)\\\\ =\frac{75}{2} (150)\\=75*75\\=5625$