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 $\color{blue}{ a = 9 }$ by the constant term $\color{blue}{c = 14} $.
$$ a \cdot c = 126 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 126 $ and add to $ b = 65 $.
Step 4: All pairs of numbers with a product of $ 126 $ are:
PRODUCT = 126 | |
1 126 | -1 -126 |
2 63 | -2 -63 |
3 42 | -3 -42 |
6 21 | -6 -21 |
7 18 | -7 -18 |
9 14 | -9 -14 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = 65 }$
PRODUCT = 126 and SUM = 65 | |
1 126 | -1 -126 |
2 63 | -2 -63 |
3 42 | -3 -42 |
6 21 | -6 -21 |
7 18 | -7 -18 |
9 14 | -9 -14 |
Step 6: Replace middle term $ 65 x $ with $ 63x+2x $:
$$ 9x^{2}+65x+14 = 9x^{2}+63x+2x+14 $$Step 7: Apply factoring by grouping. Factor $ 9x $ out of the first two terms and $ 2 $ out of the last two terms.
$$ 9x^{2}+63x+2x+14 = 9x\left(x+7\right) + 2\left(x+7\right) = \left(9x+2\right) \left(x+7\right) $$