Subtracting rational expressions with different denominators

Question

4/x - 8/x+4 - x/(x+4)^2

 

I know that the lcd of this specific equation is x(x+4)^2 , but I just do not know to multiply the lcd to each number. My webassign that I do my homework keeps saying my answer is wrong. 

Answer 1

Multiply the numerator and denominator of one fraction by one of the factors of the LCD.  Multiply the numerator and denominator of the other fraction by the other factor of the LCD.  You will end up with

 

 

[4(x + 4)² - 8x(x + 4) - x²] / [x(x + 4)²]

 

 

Now just simplify.  I leave this part to you.