Answer and step-by-step explanation:
To solve the problem, we will be using the arithmetic sequence formula which is:
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. ^^
