Question

Slope -1, passes through (0, 0)

Answer 1

Equation of a line is  y = mx + b 
m is the slope 
b is the y intercept 
It passes through points (0,0) so when x = 0 , y = 0 . So the y intercept, b = 0 
y = -1x + 0 
y = -x 
is the equation of the line