7. e and f
9. c.
sorry didn't understand 8
To find the maximum velocity you have to differentiate the function respect to r.
v = k(R - r)r^2 = kRr^2 - krr^2 = kRr^2 - kr^3
k and R are constants.
=> v' = 2kRr - 3kr^2 = kr(2R - 3r)
maximum velocity => v' = 0 => kr(2R - 3r) = 0
r = 0 or 2R - 3r = 0 => r = 2R / 3
Answer: r = 2R / 3
(3c+s)(100-20)/100=100 multiply both sides by 100
(3c+s)80=10000 divide both sides by 80
3c+s=125 subtract 3c from both sides...
s=125-3c....now let's look at the second situation...
(4c+2s)(100-40)/100=120 multiply both sides by 100
60(4c+2s)=12000 divide both sides by 60
4c+2s=200 divide both sides 2
2c+s=100 subtract 2c from both sides
s=100-2c, and from earlier we saw that s=125-3c, since s=s:
100-2c=125-3c add 3c to both sides
100+c=125 subtract 100 from both sides
c=25, and since s=100-2c
s=50
So cds cost $25.00 and sweatshirts cost $50.00
