Hello!

Recall that:
can be rewritten as:

Use the equation for the derivative of a log expression:

Substitute in the values in the expression:

Answer:
Approximately 2 months
Step-by-step explanation:
Tricia: f(d) = 5.15m + 10.25
Melanie: f(d) = 10.25m
f(d) is the total savings altogether
m is the amount of months
5.15(2) + 10.25 = 20.55
10.25(2) = 20.50
They will have the same amount of savings in approximately 2 months
1.990291 is the actual time (in months) they will be the same
Answer:
x>9
Step-by-step explanation:
-4x + 15 < -21
Subtract 15 from each side
-4x + 15-15 < -21-15
-4x < -36
Divide each side by -4, remembering to flip the inequality
-4x/-4> -36/-4
x >9
When they are collinear, they lie on the same straight line