Step 1 :
After factoring out $ 4 $ we have:
$$ 12m^{2}+20m-8 = 4 ( 3m^{2}+5m-2 ) $$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 = 5 $.
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 $\color{blue}{ b = 5 }$
PRODUCT = -6 and SUM = 5 | |
-1 6 | 1 -6 |
-2 3 | 2 -3 |
Step 7: Replace middle term $ 5 x $ with $ 6x-x $:
$$ 3x^{2}+5x-2 = 3x^{2}+6x-x-2 $$Step 8: Apply factoring by grouping. Factor $ 3x $ out of the first two terms and $ -1 $ out of the last two terms.
$$ 3x^{2}+6x-x-2 = 3x\left(x+2\right) -1\left(x+2\right) = \left(3x-1\right) \left(x+2\right) $$