Cogito
AP Calculus BC · Chapter 6 · Lesson 2
Partial Fractions
Splitting a rational function into pieces.
12 problems · about 22 minutes · FUN-6.F
Figure — use these to answer the problems
- Point(2, 0.50)
Warm Up
Straightforward practice. Get the method working first.
5 problemsA denominator with 4 distinct linear factors. How many partial fractions?
AnswerWhat must be checked before decomposing?
- That the numerator degree is lower than the denominator.
- That there are exactly two factors.
A denominator with 2 distinct linear factors. How many partial fractions?
AnswerA denominator with 3 distinct linear factors. How many partial fractions?
AnswerA factor repeated twice. How many terms does it need?
Answer
Build It Up
The same ideas with more to keep track of.
3 problemsNumerator degree 3, denominator degree 2. Divide first? 1 yes, 0 no.
AnswerEach simple partial fraction integrates to what? 1 a logarithm, 2 a polynomial.
Answerx² − 4 factors into how many linear factors?
Answer
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsPut the partial fractions process in order.
Write 1 to 4 in the boxes to put these in order.
- Check the fraction is proper, dividing first if not.
- Factor the denominator.
- Write one term per factor with unknown constants.
- Substitute the roots to find each constant.
A factor repeated three times. How many terms?
AnswerThe Constant
For 1 = A(x − 2) + B(x − 1), substituting x = 2 gives B. What is B?
AnswerThe Other One
Substituting x = 1 in the same equation gives A. What is A?
Answer