Question

Write an equation that describes the function.

Answer 1

from the points you get a slope of -1 using the slope in y=mx+b you get b=1 so y=-x+1

Answer 2

Find the slope, first:
$m = \frac{ y_{1} - y_{2} }{ x_{1} - x_{2} }$
Use any two points, for example (1,0) and (3, -2)
$m = \frac{-2 - 0}{3 - 1} = -1$
So, the slope is -1.
Then, use the formula for any given point, y and x are constants
$y - y_{1} = m(x - x_{1} )$
Use, for example, point (1, 0)
$y - 0 = (-1)(x - 1)$
$y = -x +1$
So, the equation is $y = -x +1$