The gradient/slope is undefined.
using the gradient formula, [tex]m=\frac{y2-y1}{x2-x1}[/tex],
[tex]\frac{-8-7}{-6-(-6)}[/tex]
try solving this and you'll get the answer "math error". this is because -6-(-6) is -6+6, which equals 0. anything divided by zero is infinite.
