Step 1 :
After factoring out $ 3 $ we have:
$$ 6b^{2}-39b+18 = 3 ( 2b^{2}-13b+6 ) $$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 $\color{blue}{ a = 2 }$ by the constant term $\color{blue}{c = 6} $.
$$ a \cdot c = 12 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 12 $ and add to $ b = -13 $.
Step 5: All pairs of numbers with a product of $ 12 $ are:
PRODUCT = 12 | |
1 12 | -1 -12 |
2 6 | -2 -6 |
3 4 | -3 -4 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -13 }$
PRODUCT = 12 and SUM = -13 | |
1 12 | -1 -12 |
2 6 | -2 -6 |
3 4 | -3 -4 |
Step 7: Replace middle term $ -13 x $ with $ -x-12x $:
$$ 2x^{2}-13x+6 = 2x^{2}-x-12x+6 $$Step 8: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -6 $ out of the last two terms.
$$ 2x^{2}-x-12x+6 = x\left(2x-1\right) -6\left(2x-1\right) = \left(x-6\right) \left(2x-1\right) $$