In math, the phrase "y 2x 1" is expressed as y = 2x + 1 or y = 2x - 1. Either equation is the linear formula describing a line on an x-y plane.
In the equation y = 2x + 1, the number 2 in front of the x is the slope of the line. The slope means that when the value of x increases by one, the value of y increases by two. The constant number 1 at the end of the equation is called the y-intercept, which is the value of y when the value of x is zero.