Rewrite the equation in slope-intercept form. y = mx + b
y = -2x + b
slope is -2. So substitute the given point and the slope into the general slope equation to find b
2 = -2(1) + b
4=b
Therefore, y= -2x + 4 is the equations of a line passing through point (1,2) that is parallel to 2x+y-1=0