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 = -9 $.
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 $\color{blue}{ b = -9 }$
PRODUCT = 14 and SUM = -9 | |
1 14 | -1 -14 |
2 7 | -2 -7 |
Step 6: Replace middle term $ -9 x $ with $ -2x-7x $:
$$ 2x^{2}-9x+7 = 2x^{2}-2x-7x+7 $$Step 7: Apply factoring by grouping. Factor $ 2x $ out of the first two terms and $ -7 $ out of the last two terms.
$$ 2x^{2}-2x-7x+7 = 2x\left(x-1\right) -7\left(x-1\right) = \left(2x-7\right) \left(x-1\right) $$