Answer:
2x + y + 1 = 0
This is a first degree equation with two unknown variables, x and y. They are referred to as linear equation and are typically represented in slope-intercept form, y=mx+b, where m is the slope of the line and b is the y-interecept. So you want to set the equation equal to y by isolating it to one side of the equation.
Subtract all term other than y (in this case, 2x and 1) from both sides of the equation.
2x + y + 1 - 2x - 1 = 0 - 2x - 1
y = -2x - 1