[tex]\begin{gathered} x^2-15x+2=0 \\ x^2-15x+2-2=-2 \\ x^2-15x=-2 \\ 2ab=-15 \\ 2\cdot(1)\cdot b=-15 \\ b=\frac{-15}{2\cdot1} \\ b=\frac{-15}{2} \\ x^2-15x+(\frac{-15}{2})^2=-2+(\frac{-15}{2})^2 \\ \text{the number to complete the square is }\frac{-15}{2} \end{gathered}[/tex]
