Decompose a fraction in a sum of two Let's say that I have this fraction: 2

Emilio Waters

Emilio Waters

Answered question

2022-06-03

Decompose a fraction in a sum of two
Let's say that I have this fraction:
2 x x 2 + 4 x + 3
I would like to decompose in two fraction:
A x + 3 + B x + 1
Which is the procedure for that? :)

Answer & Explanation

kaveljo49bl

kaveljo49bl

Beginner2022-06-04Added 2 answers

2 x x 2 + 4 x + 3 = 2 x x 2 + x + 3 x + 3 = 2 x x ( x + 1 ) + 3 ( x + 1 ) =
= 2 x ( x + 3 ) ( x + 1 ) = A x + 3 + B x + 1
2 x = A x + A + B x + 3 B = ( A + B ) x + A + 3 B
You needs to solve the system
A + B = 2 , A + 3 B = 0
Marlie Cole

Marlie Cole

Beginner2022-06-05Added 2 answers

x 2 + 4 x + 3 = 0
Δ = 4 2 4 1 3 = 4
x 1 , 2 = b ± Δ 2 a = 4 ± 2 2 = 3  or  1
x 2 + 4 x + 3 = ( x + 3 ) ( x + 1 )
2 x x 2 + 4 x + 3 = 2 x ( x + 3 ) ( x + 1 ) = A x + 3 + B x + 1 = A ( x + 1 ) + B ( x + 3 ) ( x + 3 ) ( x + 1 ) = ( A + B ) x + ( A + 3 B ) ( x + 3 ) ( x + 1 )
Since, 2 x ( x + 3 ) ( x + 1 ) = ( A + B ) x + ( A + 3 B ) ( x + 3 ) ( x + 1 ) ,it must be:
A + B = 2  and  A + 3 B = 0
A + 3 B = 0 A = 3 B
A + B = 2 2 B = 2 B = 1
A = 3
Therefore:
2 x x 2 + 4 x + 3 = 3 x + 3 1 x + 1

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