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 $\color{blue}{ a = 7 }$ by the constant term $\color{blue}{c = -110} $.
$$ a \cdot c = -770 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -770 $ and add to $ b = 13 $.
Step 4: All pairs of numbers with a product of $ -770 $ are:
PRODUCT = -770 | |
-1 770 | 1 -770 |
-2 385 | 2 -385 |
-5 154 | 5 -154 |
-7 110 | 7 -110 |
-10 77 | 10 -77 |
-11 70 | 11 -70 |
-14 55 | 14 -55 |
-22 35 | 22 -35 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = 13 }$
PRODUCT = -770 and SUM = 13 | |
-1 770 | 1 -770 |
-2 385 | 2 -385 |
-5 154 | 5 -154 |
-7 110 | 7 -110 |
-10 77 | 10 -77 |
-11 70 | 11 -70 |
-14 55 | 14 -55 |
-22 35 | 22 -35 |
Step 6: Replace middle term $ 13 x $ with $ 35x-22x $:
$$ 7x^{2}+13x-110 = 7x^{2}+35x-22x-110 $$Step 7: Apply factoring by grouping. Factor $ 7x $ out of the first two terms and $ -22 $ out of the last two terms.
$$ 7x^{2}+35x-22x-110 = 7x\left(x+5\right) -22\left(x+5\right) = \left(7x-22\right) \left(x+5\right) $$