[tex]n^2+7n+15=5[/tex]
[tex]n^2+7n=-10[/tex]
[tex]n^2+7n+(\frac{7}{2})^2=-10+(\frac{7}{2})^2[/tex]
[tex]n^2+7n+\frac{49}{4}=-10+\frac{49}{4}[/tex]
[tex](n+\frac{7}{2})^2=\frac{9}{4}[/tex]
[tex]n+\frac{7}{2}=\sqrt{\frac{9}{4}}[/tex]
[tex]n=-\frac{7}{2}+\sqrt{\frac{9}{4}}[/tex]
[tex]n=-2[/tex]
[tex]n=-5[/tex]
