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 = 51} $.
$$ a \cdot c = 306 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 306 $ and add to $ b = -35 $.
Step 4: All pairs of numbers with a product of $ 306 $ are:
PRODUCT = 306 | |
1 306 | -1 -306 |
2 153 | -2 -153 |
3 102 | -3 -102 |
6 51 | -6 -51 |
9 34 | -9 -34 |
17 18 | -17 -18 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -35 }$
PRODUCT = 306 and SUM = -35 | |
1 306 | -1 -306 |
2 153 | -2 -153 |
3 102 | -3 -102 |
6 51 | -6 -51 |
9 34 | -9 -34 |
17 18 | -17 -18 |
Step 6: Replace middle term $ -35 x $ with $ -17x-18x $:
$$ 6x^{2}-35x+51 = 6x^{2}-17x-18x+51 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -3 $ out of the last two terms.
$$ 6x^{2}-17x-18x+51 = x\left(6x-17\right) -3\left(6x-17\right) = \left(x-3\right) \left(6x-17\right) $$