Answer: when you write a linear equation as y = a*x, where you are relationing the numbers y to x, the rate of change from x to y is a.
then, the rate of change from -1 to 1 is the number that when multiplied by -1, turns into 1, so:
-1*a = 1
a = 1/-1 = -1
So the rate of change from x = -1 yo x = 1 is a = -1.
