1. A sequence is defined recursively using the formula $f(n+1)=-0.5 f(n)$. If the first term of the sequence is 120 , what is $f(5)$ ?
$-15$
$-7.5$
7.5
15

Step 1 ：The problem provides a recursive sequence defined by the formula \(f(n+1) = -0.5f(n)\), with the first term being 120.

Step 2 ：We are asked to find the fifth term of the sequence, denoted as \(f(5)\).

Step 3 ：To find \(f(5)\), we start with the first term and apply the formula four times.

Step 4 ：Applying the formula once, we get \(f(2) = -0.5 * 120 = -60\).

Step 5 ：Applying the formula a second time, we get \(f(3) = -0.5 * -60 = 30\).

Step 6 ：Applying the formula a third time, we get \(f(4) = -0.5 * 30 = -15\).

Step 7 ：Applying the formula a fourth time, we get \(f(5) = -0.5 * -15 = 7.5\).

Step 8 ：Thus, the fifth term of the sequence is \(\boxed{7.5}\).