Chapter P-4 is based on linear equations. Linear equations are algebraic equations of the form y = mx + b, where x and y are variables, m is the slope of the equation, and b is the constant. Linear equations intersect the y-axis at the y-intercept while the x-axis at the x-intercept. Linear equations only have one x-intercept. If we were to find an equation from a slope and two points, we use the point-slope formula, (y -y1) = m(x - x1). Then the equation will always come out to be in the form of y = mx + b.