We'll write the ratio as a sum or difference of 2
irreducible ratios in this way:
(3x-2)/(x-3)(x+1) = A/(x-3)
+ B/(x+1)
We notice that the numerator of the original
ratio is a linear function and the denominator is a quadratic
function.
The irreducible ratios from the right side have
as numerators constant functions and as denominators, linear
functions.
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)
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)
If the expressions from both sides are equal, then
the correspondent coefficients are equals:
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
B = 3 - 7/4
B =
(12-7)/4
B =
5/4
(3x-2)/(x-3)(x+1) = 74/(x-3) +
5/4(x+1)
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