Step 1 :
After factoring out $ x $ we have:
$$ 6x^{3}+x^{2}-35x = x ( 6x^{2}+x-35 ) $$Step 2 :
Step 2: 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 3: Multiply the leading coefficient $\color{blue}{ a = 6 }$ by the constant term $\color{blue}{c = -35} $.
$$ a \cdot c = -210 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -210 $ and add to $ b = 1 $.
Step 5: All pairs of numbers with a product of $ -210 $ are:
PRODUCT = -210 | |
-1 210 | 1 -210 |
-2 105 | 2 -105 |
-3 70 | 3 -70 |
-5 42 | 5 -42 |
-6 35 | 6 -35 |
-7 30 | 7 -30 |
-10 21 | 10 -21 |
-14 15 | 14 -15 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = 1 }$
PRODUCT = -210 and SUM = 1 | |
-1 210 | 1 -210 |
-2 105 | 2 -105 |
-3 70 | 3 -70 |
-5 42 | 5 -42 |
-6 35 | 6 -35 |
-7 30 | 7 -30 |
-10 21 | 10 -21 |
-14 15 | 14 -15 |
Step 7: Replace middle term $ 1 x $ with $ 15x-14x $:
$$ 6x^{2}+x-35 = 6x^{2}+15x-14x-35 $$Step 8: Apply factoring by grouping. Factor $ 3x $ out of the first two terms and $ -7 $ out of the last two terms.
$$ 6x^{2}+15x-14x-35 = 3x\left(2x+5\right) -7\left(2x+5\right) = \left(3x-7\right) \left(2x+5\right) $$