Final answer:
The expression an=-7(n-1)(3) simplifies to an=-21n+21 by distributing the multiplication, with no further simplifications needed.
Step-by-step explanation:
To simplify the expression an=-7(n-1)(3), we need to distribute the multiplication across the terms within the parenthesis.
Multiplying -7 by 3 gives us -21.
Now, we distribute -21 to each term inside the parentheses (n-1). This results in an = -21n + 21.
There is no further simplification possible since the expression is already in its simplest form. Hence, the simplified expression for an = -7(n-1)(3) is an = -21n + 21.
Remember to eliminate terms wherever possible to simplify the algebra and check the answer to see if it is reasonable.