Monday, May 11, 2015

Write the fraction (3x-2)/(x-3)(x+1) as partial fractions.

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.

No comments:

Post a Comment

Calculate tan(x-y), if sin x=1/2 and sin y=1/3. 0

We'll write the formula of the tangent of difference of 2 angles. tan (x-y) = (tan x - tan y)/(1 + tan x*tan y) ...