Step 1 :
After factoring out $ 2 $ we have:
$$ 6x^{2}-2x-4 = 2 ( 3x^{2}-x-2 ) $$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 = -2} $.
$$ a \cdot c = -6 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -6 $ and add to $ b = -1 $.
Step 5: All pairs of numbers with a product of $ -6 $ are:
PRODUCT = -6 | |
-1 6 | 1 -6 |
-2 3 | 2 -3 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -1 }$
PRODUCT = -6 and SUM = -1 | |
-1 6 | 1 -6 |
-2 3 | 2 -3 |
Step 7: Replace middle term $ -1 x $ with $ 2x-3x $:
$$ 3x^{2}-x-2 = 3x^{2}+2x-3x-2 $$Step 8: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -1 $ out of the last two terms.
$$ 3x^{2}+2x-3x-2 = x\left(3x+2\right) -1\left(3x+2\right) = \left(x-1\right) \left(3x+2\right) $$