Step 1 :
After factoring out $ -1 $ we have:
$$ -5x^{2}+23x+10 = - ~ ( 5x^{2}-23x-10 ) $$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 = -10} $.
$$ a \cdot c = -50 $$Step 4: Find out two numbers that multiply to $ a \cdot c = -50 $ and add to $ b = -23 $.
Step 5: All pairs of numbers with a product of $ -50 $ are:
PRODUCT = -50 | |
-1 50 | 1 -50 |
-2 25 | 2 -25 |
-5 10 | 5 -10 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -23 }$
PRODUCT = -50 and SUM = -23 | |
-1 50 | 1 -50 |
-2 25 | 2 -25 |
-5 10 | 5 -10 |
Step 7: Replace middle term $ -23 x $ with $ 2x-25x $:
$$ 5x^{2}-23x-10 = 5x^{2}+2x-25x-10 $$Step 8: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -5 $ out of the last two terms.
$$ 5x^{2}+2x-25x-10 = x\left(5x+2\right) -5\left(5x+2\right) = \left(x-5\right) \left(5x+2\right) $$