How do we find surface area & lateral area of prism and cylinder

to find the surface area and the later area of both a cylinder and a prism we nee to know a few formulas:

• LA= ph [lateral area]
• SA= LA+2B (only for prisms and cylinders) [surface area]

 these are examples in which we can use these formulas:
 

 the formula of the lateral area is used to help find the surface area. say we had acylinder with the radius of 2cm and the height of 3cm.

1. we need to find the perimeter of the circle which is 2πr multiplied by the height which will make it 12π or 37.7cm
2. then we πr² * 2 which is 8π or 25.13cm
3. now we multiply these two answers to give of the  surface area of the cylinder which is 947.401cm²  

for more help or to try it out here are some links:

• http://www.teacherschoice.com.au/maths_library/area%20and%20sa/area_9.htm 
• http://hotmath.com/help/gt/genericprealg/section_9_4.html 
• http://www.andrews.edu/~calkins/math/webtexts/geom10.htm 
• http://www.youtube.com/watch?v=tbA-9CBaB8A 

How do we do composition

to find that what is composition we first need to know the formula.
(f*g)(x)=f(g(x))
now that we know the formula it will be easy to answer the following question.

1.) given f(x) = 4x+6  and (g)x = (x^2+4)

• we will start by writing 4x+6 but replace the x with x^2+4 like so 4(x^2+4)+6 

• disstribute the 4 in the beginning within the parentheses.
  
• we will get 4x^2+16+6 , then 16+6=22
  
• the answer will be 4x^2+22

2.) now try on your own  given f(x) = 2x+9 and (g)x = (x^2+7)