It seems that $ -5x^{2}+6x+15 $ cannot be factored out.
Step 1 :
After factoring out $ -1 $ we have:
$$ -5x^{2}+6x+15 = - ~ ( 5x^{2}-6x-15 ) $$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 $\color{blue}{ a = 5 }$ by the constant term $\color{blue}{c = -15} $.
$$ a \cdot c = -75 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -75 $ and add to $ b = -6 $.
Step 5: All pairs of numbers with a product of $ -75 $ are:
PRODUCT = -75 | |
-1 75 | 1 -75 |
-3 25 | 3 -25 |
-5 15 | 5 -15 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -6 }$
Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ -6 }$, we conclude the polynomial cannot be factored.