Step 1 :
After factoring out $ 2x $ we have:
$$ 12x^{3}-14x^{2}-30x = 2x ( 6x^{2}-7x-15 ) $$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 $\color{blue}{ a = 6 }$ by the constant term $\color{blue}{c = -15} $.
$$ a \cdot c = -90 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -90 $ and add to $ b = -7 $.
Step 5: All pairs of numbers with a product of $ -90 $ are:
PRODUCT = -90 | |
-1 90 | 1 -90 |
-2 45 | 2 -45 |
-3 30 | 3 -30 |
-5 18 | 5 -18 |
-6 15 | 6 -15 |
-9 10 | 9 -10 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -7 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ -7 }$, we conclude the polynomial cannot be factored.