November 25, 2015

Homework Help: Algebra

Posted by Angel007 on Sunday, August 7, 2005 at 1:15pm.

Find the LCD for the given rational expressions, and convert each rational expression into an equivalent rational expression with the LCD as the denominator. 3 5
----, ----
84a 63b

4b 6
-----, ----
75a 105ab

Can someone here help me I do not understand this at all need help!

Your types question got the fractions all scrmbled. I will assume the fractions you are trying to find the LCD for are
3/(84 a), 5/(63 b), 4b/(75 a) , and 6/(105 ab)

To get the LCD, factor all the demominators into prime factors, plus the algebraic characters a and b.
84 a -> 2*2*2*3*7 a
63 b -> 3*3*7 b
75 a -> 3*5*5 a
105 ab -> 3*5*7 a b

The LCD must contain all the prime factors for as many times as they occur in the term that has the most of them. You end up with
LCD = 2*2*2*3*3*5*5*7 a b
= 12,600 a b

3/(84 a) = 450 b/12,600 ab
5/(63 b) = 1000 a/12,600 ab
4b/(75 a) = 672 b/12,600 ab
6/(105 ab) = 720/12,600 ab

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