Step 1 :
After factoring out $ 3 $ we have:
$$ 12x^{2}-9x+15 = 3 ( 4x^{2}-3x+5 ) $$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 $\color{blue}{ a = 4 }$ by the constant term $\color{blue}{c = 5} $.
$$ a \cdot c = 20 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 20 $ and add to $ b = -3 $.
Step 5: All pairs of numbers with a product of $ 20 $ are:
PRODUCT = 20 | |
1 20 | -1 -20 |
2 10 | -2 -10 |
4 5 | -4 -5 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -3 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ -3 }$, we conclude the polynomial cannot be factored.