Final answer:
To find the first term (a1) of the geometric sequence, use the formula a_n = a1 * r^(n-1). Plug in the given values and solve for a1.
Step-by-step explanation:
To find the first term (a1) of the geometric sequence, we can use the formula an = a1 * r^(n-1), where an is any term of the sequence, a1 is the first term, and r is the common ratio.
In this case, we are given a3 = 4 and r = 2. Plugging these values into the formula, we get:
4 = a1 * 2^(3-1)
Simplifying this equation, we find:
4 = 4a1
Dividing both sides of the equation by 4, we find:
a1 = 1
Therefore, the first term of the geometric sequence is a1 = 1.