Step 1 :
After factoring out $ -2 $ we have:
$$ -6x^{2}-24x-40 = -2 ( 3x^{2}+12x+20 ) $$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 $\color{blue}{ a = 3 }$ by the constant term $\color{blue}{c = 20} $.
$$ a \cdot c = 60 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 60 $ and add to $ b = 12 $.
Step 5: All pairs of numbers with a product of $ 60 $ are:
PRODUCT = 60 | |
1 60 | -1 -60 |
2 30 | -2 -30 |
3 20 | -3 -20 |
4 15 | -4 -15 |
5 12 | -5 -12 |
6 10 | -6 -10 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = 12 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ 12 }$, we conclude the polynomial cannot be factored.