Step 1 :

After factoring out $ -4 $ we have:

$$ -20r^{2}+12r+12 = -4 ( 5r^{2}-3r-3 ) $$

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:

$$ a = 5 , b = -3 ~ \text{ and } ~ c = -3 $$

Step 3: Multiply the leading coefficient $\color{blue}{ a = 5 }$ by the constant term $\color{blue}{c = -3} $.

$$ a \cdot c = -15 $$

Step 4: Find out two numbers that multiply to $ a \cdot c = -15 $ and add to $ b = -3 $.

Step 5: All pairs of numbers with a product of $ -15 $ are:

PRODUCT = -15
-1     15	1     -15
-3     5	3     -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.

Polynomial Factoring Calculator