7.8 Partial Fractions
If we wanted to add something like this: We would need to find a common denominator! Now, we want to REVERSE the process! Go from here, to here!
This process is called partial fraction decomposition. Steps: (1) Factor the denominator (2) Express as two (or more) fractions with A & B (or more) as placeholders for the numerators (3) Multiply both sides by LCD (4) Solve for A & B (or more) by letting x equal values that would make the other letter be multiplied by 0 (5) Substitute A & B (sometimes simple, sometimes not!)
For all examples, decompose into partial fractions. Ex 1)
Ex 2) x(x 2 – 2x – 15)
If (x – a) n is a factor of the denominator, you will need (x – a), (x – a) 2, …, (x – a) n Ex 3) To solve for B, use A & C & let x = 0:
Ex 4) Factor bottom! 16 1 –10 3 ↓ –3 0 6x 2 + 7x – 3 6x 2 + 9x – 2x – 3 3x(2x + 3) – 1(2x + 3) (3x – 1)(2x + 3) denom = (x – 1)(3x – 1)(2x + 3) –18 7 –29
Ex 4) cont…
Homework #708 Pg 378 #1, 5, 7, 18, 21, 29