TUTORIALS:
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Adding or Subtracting Rational Expressions with Different Denominators
Here is the procedure for adding (or subtracting) fractions.
Procedure
To Add or Subtract Rational Expressions
That Have Different Denominators
Step 1 Find the LCD.
Step 2 Rewrite each rational expression with the LCD as the
denominator.
Step 3 Add or subtract the numerators.
The denominator stays the same.
Step 4 Reduce to lowest terms.
Example
Add:
Step 4 Reduce.
The numerator cannot be factored. This rational expression is in lowest
terms.
We will leave the denominator in factored form.
So, the result is
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Note:
To factor 5x2 - 3x - 2:
• Find two integers whose product is
5(-2) = -10, and whose sum is -3.
They are 2 and -5.
• Use these integers to rewrite
5x2 - 3x - 2
as
5x2 + 2x - 5x - 2.
• Factor by grouping.
x(5x + 2) - 1(5x + 2)
= (5x + 2)(x + 1)
To factor x2 + 5x - 6:
• Find two integers whose product is -6 and whose sum is 5.
They are -1 and 6.
• Use these integers to write the
factorization (x - 1)(x + 6).
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