Consider the equation $3x + y - z = 6$.

1. Sketch a graph.

   Hint (a):

   Notice that there are three variables. Find the three intercepts.

   Answer (a):

   

2. Is $\left(1, 2, –1\right)$ on the graph? Justify your answer.

   Hint (b):

   Does the point make the equation true?

   Answer (b):

   Yes, it is a solution to the equation.