- #1
paul34
- 6
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This is probably a "basic" question, but I can't seem to remember how to do partial fractions problems where there is only a 1 in the numerator.
For example (just making this up), let's say I have:
1/s(s+4)(s+5)
So what I'd do is 1/s(s+4)(s+5) = A/s + B/(s+4) + C/(s+5) as one would expect, but this can't be right, correct? It seems a lot of coefficients don't "work out."
For example, after doing cross multiplications and combining terms, you would basically get:
For s^2 terms: (A+B+C) = 0 [1]
For s terms: (6A + 5B + 4C) = 0 [2]
For no-s terms: 5A = 1 [3]
Then putting [3]--> [1], then getting B=-C - 1/5, and putting that in [2]. You'll end up with A being equal to 1/5, and C being equal to -1/5. Plug this all into [1], so then that means B is equal to zero. What am I missing here? Is this right?
Matlab says it should be C=-1 and B=1, which means that A is zero then? Huh? I am pretty confused.
Thanks.
For example (just making this up), let's say I have:
1/s(s+4)(s+5)
So what I'd do is 1/s(s+4)(s+5) = A/s + B/(s+4) + C/(s+5) as one would expect, but this can't be right, correct? It seems a lot of coefficients don't "work out."
For example, after doing cross multiplications and combining terms, you would basically get:
For s^2 terms: (A+B+C) = 0 [1]
For s terms: (6A + 5B + 4C) = 0 [2]
For no-s terms: 5A = 1 [3]
Then putting [3]--> [1], then getting B=-C - 1/5, and putting that in [2]. You'll end up with A being equal to 1/5, and C being equal to -1/5. Plug this all into [1], so then that means B is equal to zero. What am I missing here? Is this right?
Matlab says it should be C=-1 and B=1, which means that A is zero then? Huh? I am pretty confused.
Thanks.
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