We'll decompose the rational function in partial
quotients:
(3x-2)/(x-3)(x+1) = A/(x-3) +
B/(x+1)
We'll calculate LCD of the 2 ratios from the right
side.
The LCD is the same with the denominator from the
left side.
LCD =
(x-3)(x+1)
We'll multiply both sides by (x-3)(x+1) and the
expression will become:
(3x-2) = A(x+1) +
B(x-3)
We'll remove the
brackets:
3x - 2 = Ax + A + Bx -
3B
We'll combine like terms form the right
side:
3x - 2 = x(A+B) +
(A-3B)
We'll compare and we'll
get:
3 = A+B
-2 = A -
3B
We'll use the symmetric
property:
A+B = 3 (1)
A - 3B =
-2 (2)
We'll multiply (1) by
3:
3A+3B = 9 (3)
We'll add (3)
to (2):
3A+3B+A - 3B =
9-2
We'll eliminate like
terms:
4A = 7
We'll divide by
4:
A = 7/4
We'll substitute A
in (1):
A+B = 3
7/4 + B =
3
We'll subtract 7/4 both
sides:
B = 3 - 7/4 => B = (12-7)/4 => B =
5/4
The fraction (3x-2)/(x-3)(x+1) = 7/4(x-3)
+ 5/4(x+1), where 7/4(x-3) and 5/4(x+1) are partial
fractions.
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