Question

Two terms of an arithmetic sequence are a10=16 and a35=66 find the sum of the first 75 terms

Answer 1

The sum of the first 75 terms of the arithmetic sequence that has 10th term as 16 and the 35th term as 66 is 5400.  

How to find the sum of terms using Arithmetic sequence formula

aₙ = a + (n - 1)d

where

• a = first term

• d = common difference

• n = number of terms

Therefore, let's find a and d

a₁₀ = a + (10 - 1)d

a₃₅ = a + (35 - 1)d

Hence,

16 = a + 9d

66 = a + 34d

25d = 50

d = 50 / 25

d = 2

16 - 9(2) = a

a = 16 - 18

a  = -2

Therefore, let's find the sum of 75 terms of the arithmetic sequence

Sₙ = n / 2 (2a + (n - 1)d)

S₇₅ = 75 / 2 (2(-2) + (75 - 1)2)

S₇₅ = 37.5 (-4 + 148)

S₇₅ = 37.5(144)

S₇₅ = 5400

learn more on arithmetic sequence here: brainly.com/question/1687271