Question

Partial fraction decomposition
20x+9/25x^2+20x+4

Answer 1

Step-by-step explanation:

We have

$\frac{20x + 9}{25 {x}^{2} + 20x + 4 }$

Let's factor the denomiator first,

the denomaitor is a perfect square so we get

$\frac{20x + 9}{(5x + 2) {}^{2} }$

Now, we must think of two fractions that

$\frac{a}{(5x + 2) {}^{2} } + \frac{b}{5x + 2}$

We use a perfect square term for one fraction, then a linear one for the next, because if we set both of the denomiator to the same factor, we would get a inconsistent system.

So right now, we have

$\frac{a}{(5x + 2) { }^{2} } + \frac{b}{5x + 2} = \frac{20x +9 }{25 {x}^{2} + 20x + 4 }$

$a + (5x + 2)b = 20x + 9$

$5b (x)= 20$

$a + 2b = 9$

$b = 4$

so that means that a is

$a + (2)(4) = 9$

$a + 8 = 9$

$a = 1$

So our equation is

$\frac{1}{(5x + 2) {}^{2} } + \frac{4}{5x + 2}$