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 $\color{blue}{ a = 2 }$ by the constant term $\color{blue}{c = -7} $.
$$ a \cdot c = -14 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -14 $ and add to $ b = -13 $.
Step 4: All pairs of numbers with a product of $ -14 $ are:
PRODUCT = -14 | |
-1 14 | 1 -14 |
-2 7 | 2 -7 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -13 }$
PRODUCT = -14 and SUM = -13 | |
-1 14 | 1 -14 |
-2 7 | 2 -7 |
Step 6: Replace middle term $ -13 x $ with $ x-14x $:
$$ 2x^{2}-13x-7 = 2x^{2}+x-14x-7 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -7 $ out of the last two terms.
$$ 2x^{2}+x-14x-7 = x\left(2x+1\right) -7\left(2x+1\right) = \left(x-7\right) \left(2x+1\right) $$