Step 1 :
After factoring out $ -x $ we have:
$$ -19x^{3}-5x^{2}+8x = -x ( 19x^{2}+5x-8 ) $$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 $\color{blue}{ a = 19 }$ by the constant term $\color{blue}{c = -8} $.
$$ a \cdot c = -152 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -152 $ and add to $ b = 5 $.
Step 5: All pairs of numbers with a product of $ -152 $ are:
PRODUCT = -152 | |
-1 152 | 1 -152 |
-2 76 | 2 -76 |
-4 38 | 4 -38 |
-8 19 | 8 -19 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = 5 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ 5 }$, we conclude the polynomial cannot be factored.