Answer:
To find the value of a4, we need to use the recursive formula for the sequence. The formula gives us the nth term in the sequence in terms of the (n-1)th term.
We are given that a1 = -7, so we can use the recursive formula to find a2, a3, and a4:
a2 = a1 - 4 = -7 - 4 = -11
a3 = a2 - 4 = -11 - 4 = -15
a4 = a3 - 4 = -15 - 4 = -19
Therefore, the value of a4 is -19.