Question

For what values of a is the point M(−3a, 1+a) on the graph of y=−x+3?

Answer 1

If the point lies on the graph of the equation

`y=-x+3`

Then the y coordinate must be the opposite of the x coordinate, plus 3:

`1+a = -(-3a)+3 \iff 1+a=3a+3 \iff 2a=-2 \iff a=-1`