how do we add &subtarct rational expression?

Add and Subtract rational expression is so easy
take 3/2k^2+5/2k^2

1. all we really have to do it add the top and keep the denominator the same.
   So this rational expression really is 3+5/2k^2
2. now our final answer will be 8/2k^2 

here is another example 3/4+1/8

1. we must have common denominator
   what is the least common denominator... it 8
   4: 4,8,12,16,20,24,28,32,36,40
   8; 8,16,24,32,40
2. we need to multiply 3/4's denominator by 2 to make to make it 8
   this will make this fraction into 6/8
3. finally we can add this to fractions together giving us the answer of 7/8

for more help check out the links below.

• http://www.youtube.com/watch?v=FZdt73khrxA&feature=relmfu
• http://www.purplemath.com/modules/rtnladd.htm