Verified answer

Answer and step-by-step explanation:

To solve the problem, we will be using the arithmetic sequence formula which is:

• An = A1 + (n - 1)d

where

An is the nth/last term,

A1 is the first term,

n is the number of terms and

d is the common difference.

Let's substitute the values to the formula.

A45 = 20 => 45th term

A1 = A1

n = 45

d = 1/2

20 = A1 + (45 - 1)(1/2) => substitute and subtract 1 from 45

20 = A1 + (44)(1/2) => multiply 44 by 1/2.

20 = A1 + 22 => isolate A1 by subtracting 22 to both sides of the equation

20 - 22 = A1 + 22 - 22 => simplify

-2 = A1

Therefore, the first term is -2.

*If you have some part/s you want me to clarify, please comment below. ^^