Step 1: 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 2: Multiply the leading coefficient $\color{blue}{ a = 5 }$ by the constant term $\color{blue}{c = -22} $.
$$ a \cdot c = -110 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -110 $ and add to $ b = -1 $.
Step 4: All pairs of numbers with a product of $ -110 $ are:
PRODUCT = -110 | |
-1 110 | 1 -110 |
-2 55 | 2 -55 |
-5 22 | 5 -22 |
-10 11 | 10 -11 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -1 }$
PRODUCT = -110 and SUM = -1 | |
-1 110 | 1 -110 |
-2 55 | 2 -55 |
-5 22 | 5 -22 |
-10 11 | 10 -11 |
Step 6: Replace middle term $ -1 x $ with $ 10x-11x $:
$$ 5x^{2}-x-22 = 5x^{2}+10x-11x-22 $$Step 7: Apply factoring by grouping. Factor $ 5x $ out of the first two terms and $ -11 $ out of the last two terms.
$$ 5x^{2}+10x-11x-22 = 5x\left(x+2\right) -11\left(x+2\right) = \left(5x-11\right) \left(x+2\right) $$