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02.06.2018: One Lesson of Math - Multiplying and Dividing Rational Expressions, Part 1


Today's soundtrack is Spawn of Possession: Cabinet, a brutal technical death metal album with insane drumming.


This evening, I'm moving on to the next chapter of the unit about rational expressions. I'll now be learning how to multiply and divide rational expressions.


There are three skills that I will be learning:

  1. How to multiply rational expressions

  2. How to divide rational expressions

  3. How to factor before simplifying rational expressions


We can refer to the first two as "simplifying," a catch-all phrase that encompasses finding either product or quotient. If our polynomial expressions are binomials or trinomials, we can factor prior to simplifying.


Let's go through the steps for each.

 

How to Multiply Rational Expressions

  1. Determine all non-permissible values of each expression

  2. Divide "numerators and denominators by their common factors" (Pearson's Pre-Calculus 11, p. 534)

  3. Multiply the numerators

  4. Multiply the denominators

How to Divide Rational Expressions

  1. Determine all non-permissible values of each expression

  2. Flip the second expression to get its reciprocal

  3. Determine all non-permissible values of the flipped expression

  • We have to do this so that we do not divide by zero

  1. Divide "numerators and denominators by their common factors" (Pearson's, p. 534)

  2. Multiply the numerators

  3. Multiply the denominators

How to Factor Before Simplifying Rational Expressions

  1. Determine all non-permissible values of each expression

  2. Convert any binomials and trinomials to factored form

  3. Simplify

  4. If multiplying, proceed from step 2 in "How to Multiply Rational Expressions"

  5. If dividing, proceed from step 2 in "How to Divide Rational Expressions"

 

That's all for tonight! Next time, I'll be working on the assignment portion of this lesson.

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