Step 1: 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 2: Multiply the leading coefficient $\color{blue}{ a = 6 }$ by the constant term $\color{blue}{c = 5} $.
$$ a \cdot c = 30 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 30 $ and add to $ b = -31 $.
Step 4: All pairs of numbers with a product of $ 30 $ are:
PRODUCT = 30 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -31 }$
PRODUCT = 30 and SUM = -31 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 6: Replace middle term $ -31 x $ with $ -x-30x $:
$$ 6x^{2}-31x+5 = 6x^{2}-x-30x+5 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -5 $ out of the last two terms.
$$ 6x^{2}-x-30x+5 = x\left(6x-1\right) -5\left(6x-1\right) = \left(x-5\right) \left(6x-1\right) $$