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 $\color{blue}{ a = 6 }$ by the constant term $\color{blue}{c = 49} $.
$$ a \cdot c = 294 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 294 $ and add to $ b = 35 $.
Step 4: All pairs of numbers with a product of $ 294 $ are:
PRODUCT = 294 | |
1 294 | -1 -294 |
2 147 | -2 -147 |
3 98 | -3 -98 |
6 49 | -6 -49 |
7 42 | -7 -42 |
14 21 | -14 -21 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = 35 }$
PRODUCT = 294 and SUM = 35 | |
1 294 | -1 -294 |
2 147 | -2 -147 |
3 98 | -3 -98 |
6 49 | -6 -49 |
7 42 | -7 -42 |
14 21 | -14 -21 |
Step 6: Replace middle term $ 35 x $ with $ 21x+14x $:
$$ 6x^{2}+35x+49 = 6x^{2}+21x+14x+49 $$Step 7: Apply factoring by grouping. Factor $ 3x $ out of the first two terms and $ 7 $ out of the last two terms.
$$ 6x^{2}+21x+14x+49 = 3x\left(2x+7\right) + 7\left(2x+7\right) = \left(3x+7\right) \left(2x+7\right) $$