Answer:
C(t) = -x^2 + 5
Explanation:
Notice how C(t) = 5 when t = 0. This means that (0, 5) is a point on C(t) and is the y-intercept, thus making the constant term (term without variable in standard form) 5. Next, notice how C(t) decreases as t increases and decreases. This means that C(t) is reflected over the x-axis such that it looks like an upside-down U shape. Thus, a negative must be applied to the term of the highest degree.