11.
V=pir^2h
V=pi*(5x+2)*(2x+8)
Distribute
(pi*5x*pi*2)(2x+8)
Apply the foil method (a+b)(c+d)=ac+ad+bc+bd
10pix^2+40pix+4pix+16x
Simplify
10pix^2+44pix+16pi
12.
S=4pir^2
S=4pi(3x+2)^2
Use square of sum (a+b)^2=a^2+2ab+b^2
4pi((3x)^2+2*3x*2+2^2)
2. Use multiplication distributive property (xy)^a=x^ay^a
4pi(3^2x^2+2*3x*2+2^2)
Simplify 3^2 to 9
4pi(9x^2+2*3x*2+2^2)
Simplify 2^2 to 4
4pi(9x^2+2*3x*2+4)
Simplify 2*3x*2 to 12x
4pi(9x^2+12x+4)
Distribute
36pix^2+48pix+16pi
Have a nice day :D
