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 = -10} $.
$$ a \cdot c = -20 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -20 $ and add to $ b = 19 $.
Step 4: All pairs of numbers with a product of $ -20 $ are:
PRODUCT = -20 | |
-1 20 | 1 -20 |
-2 10 | 2 -10 |
-4 5 | 4 -5 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = 19 }$
PRODUCT = -20 and SUM = 19 | |
-1 20 | 1 -20 |
-2 10 | 2 -10 |
-4 5 | 4 -5 |
Step 6: Replace middle term $ 19 x $ with $ 20x-x $:
$$ 2x^{2}+19x-10 = 2x^{2}+20x-x-10 $$Step 7: Apply factoring by grouping. Factor $ 2x $ out of the first two terms and $ -1 $ out of the last two terms.
$$ 2x^{2}+20x-x-10 = 2x\left(x+10\right) -1\left(x+10\right) = \left(2x-1\right) \left(x+10\right) $$