Hello,
which principle?
f(x)=-x²+2x
==>f'(x)= -2x+2
You mean maybe this

f(x+h)=-(x+h)²+2(x+h)= -(x²+2hx+h²)+2x+2h
f(x)=-x²+2x
Circumference = 2 * pi * r, where r is the radius
For this circle, the circumference is 11pi, so 11pi=2*pi*radius. Divide both sides by 2pi and you get r is = to 5.5 inches.
Area of a circle is pi*r^2. Since we just saw that r = 5.5 inches, the circle has an area of 5.5 inches * 5.5 inches * pi or 30.25 pi inches squared.
I suppose you're supposed to convert 100111 from base 2 to base 10. We have

so the missing number is 39.
Start with your lowest numbers, 3 bracelets have 24 beads. The easiest way to find your answer is to find out how many beads are on 1 bracelet. So 24/3 will give us that answer. 24/3=8. and then multiply 7 by 8 to get 56. then check your answer to make sure it fits.
3 x 8 = 24
5 x 8 = 40
7 x 8 = 56
9 x 8 = 72