Step 1 :
After factoring out $ x^{2} $ we have:
$$ x^{5}-125x^{2} = x^{2} ( x^{3}-125 ) $$Step 2 :
To factor $ x^{3}-125 $ we can use difference of cubes formula:
$$ I^3 - II^3 = (I - II)(I^2 + I \cdot II + II^2) $$After putting $ I = x $ and $ II = 5 $ , we have:
$$ x^{3}-125 = ( x-5 ) ( x^{2}+5x+25 ) $$Step 3 :
Step 3: Identify constants $ \color{blue}{ b }$ and $\color{red}{ c }$. ( $ \color{blue}{ b }$ is a number in front of the $ x $ term and $ \color{red}{ c } $ is a constant). In our case:
$$ \color{blue}{ b = 5 } ~ \text{ and } ~ \color{red}{ c = 25 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 5 } $ and multiply to $ \color{red}{ 25 } $.
Step 4: Find out pairs of numbers with a product of $\color{red}{ c = 25 }$.
PRODUCT = 25 | |
1 25 | -1 -25 |
5 5 | -5 -5 |
Step 5: Because none of these pairs will give us a sum of $ \color{blue}{ 5 }$, we conclude the polynomial cannot be factored.