The sum of the first 21 terms of the progression, - 18,-15,-12is?

Aboat's value over time is given as the function f(x) and graphed below. use a(x) = 400(b)x + 0 as the parent function. which graph shows the boat's value increasing at a rate of 25% per year?

How do i do this activity, is appreciated

The power generated by an electrical circuit (in watts) as a function of its current c (in amperes) is modeled by p(c)= -15c(c-8) what current will produce the maximum power?