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 $\color{blue}{ a = 3 }$ by the constant term $\color{blue}{c = 10} $.
$$ a \cdot c = 30 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 30 $ and add to $ b = 13 $.
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 $\color{blue}{ b = 13 }$
PRODUCT = 30 and SUM = 13 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 6: Replace middle term $ 13 x $ with $ 10x+3x $:
$$ 3x^{2}+13x+10 = 3x^{2}+10x+3x+10 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ 1 $ out of the last two terms.
$$ 3x^{2}+10x+3x+10 = x\left(3x+10\right) + 1\left(3x+10\right) = \left(x+1\right) \left(3x+10\right) $$