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 = -247} $.
$$ a \cdot c = -494 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -494 $ and add to $ b = -25 $.
Step 4: All pairs of numbers with a product of $ -494 $ are:
PRODUCT = -494 | |
-1 494 | 1 -494 |
-2 247 | 2 -247 |
-13 38 | 13 -38 |
-19 26 | 19 -26 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -25 }$
PRODUCT = -494 and SUM = -25 | |
-1 494 | 1 -494 |
-2 247 | 2 -247 |
-13 38 | 13 -38 |
-19 26 | 19 -26 |
Step 6: Replace middle term $ -25 x $ with $ 13x-38x $:
$$ 2x^{2}-25x-247 = 2x^{2}+13x-38x-247 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -19 $ out of the last two terms.
$$ 2x^{2}+13x-38x-247 = x\left(2x+13\right) -19\left(2x+13\right) = \left(x-19\right) \left(2x+13\right) $$