Work Step by Step
The first question to ask yourself is what two numbers multiply to -18 while adding to 3? 6 and -3 are the two numbers that satisfy this. We need a $x$$\times$$x$ to get $x^2$. Also, we need an $y$$\times$$y$ to get $y^2$. The $y^2$ is connected to the -18 so we know that one $y$ will be connected to the 6 and one $y$ will be connected to the -3. This setup will naturally form to get $3xy$.