Step 1 :
After factoring out $ 5x $ we have:
$$ 125x^{3}+75x^{2}+15x = 5x ( 25x^{2}+15x+3 ) $$Step 2 :
Step 2: Identify constants $ a $ , $ b $ and $ c $.
$ a $ is a number in front of the $ x^2 $ term $ b $ is a number in front of the $ x $ term and $ c $ is a constant. In this case:
Step 3: Multiply the leading coefficient $\color{blue}{ a = 25 }$ by the constant term $\color{blue}{c = 3} $.
$$ a \cdot c = 75 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 75 $ and add to $ b = 15 $.
Step 5: All pairs of numbers with a product of $ 75 $ are:
PRODUCT = 75 | |
1 75 | -1 -75 |
3 25 | -3 -25 |
5 15 | -5 -15 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = 15 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ 15 }$, we conclude the polynomial cannot be factored.