1. write out your equation
[tex]x(x + 3) = 18[/tex]
2. distribute
[tex](x \times x) + (3 \times x) = 18[/tex]
Simplify
[tex]{x}^{2} + 3x = 18[/tex]
Move all terms to one side
[tex]{x}^{2} + 3x - 18 = 0[/tex]
Factor
[tex](x - 3)(x + 6) = 0[/tex]
Substitute x so the equation equals zero
[tex]x = 3[/tex]
[tex]x = - 6[/tex]
