Step 1 :
After factoring out $ 9 $ we have:
$$ 9j^{2}+27j-90 = 9 ( j^{2}+3j-10 ) $$Step 2 :
Step 2: Identify constants $ \color{blue}{ b }$ and $\color{red}{ c }$. ( $ \color{blue}{ b }$ is a number in front of the $ x $ term and $ \color{red}{ c } $ is a constant). In our case:
$$ \color{blue}{ b = 3 } ~ \text{ and } ~ \color{red}{ c = -10 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 3 } $ and multiply to $ \color{red}{ -10 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = -10 }$.
PRODUCT = -10 | |
-1 10 | 1 -10 |
-2 5 | 2 -5 |
Step 4: Find out which pair sums up to $\color{blue}{ b = 3 }$
PRODUCT = -10 and SUM = 3 | |
-1 10 | 1 -10 |
-2 5 | 2 -5 |
Step 5: Put -2 and 5 into placeholders to get factored form.
$$ \begin{aligned} j^{2}+3j-10 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ j^{2}+3j-10 & = (x -2)(x + 5) \end{aligned} $$