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