Answer:
y = - 2x
Step-by-step explanation:
The equation of a line passing through the origin is
y = mx ← m is the slope
To calculate m use the slope formula
m = ( y₂ - y₁ ) / ( x₂ - x₁ )
with (x₁, y₁ ) = (- 1, 2) and (x₂, y₂ ) = (0, 0) ← 2 points on the line
m = 
= 
= - 2
y = - 2x ← equation of line
