Step 1 :
After factoring out $ 2 $ we have:
$$ 6x^{2}-16x-6 = 2 ( 3x^{2}-8x-3 ) $$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 $\color{blue}{ a = 3 }$ by the constant term $\color{blue}{c = -3} $.
$$ a \cdot c = -9 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -9 $ and add to $ b = -8 $.
Step 5: All pairs of numbers with a product of $ -9 $ are:
PRODUCT = -9 | |
-1 9 | 1 -9 |
-3 3 | 3 -3 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -8 }$
PRODUCT = -9 and SUM = -8 | |
-1 9 | 1 -9 |
-3 3 | 3 -3 |
Step 7: Replace middle term $ -8 x $ with $ x-9x $:
$$ 3x^{2}-8x-3 = 3x^{2}+x-9x-3 $$Step 8: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -3 $ out of the last two terms.
$$ 3x^{2}+x-9x-3 = x\left(3x+1\right) -3\left(3x+1\right) = \left(x-3\right) \left(3x+1\right) $$