What conic section is defined by all points in a plane where the difference between the lengths of segments x and y remains constant?

  hyperbola

Step-by-step explanation:

If the sum is constant, the figure is an ellipse.

If the difference is constant, you get a hyperbola.

If one length is constant, you get a circle.

If the length to a point is the same as the length to a line, you get a parabola.

b

step-by-step explanation:

a difference is the result of subtraction. while each of these expressions has subtraction in it, a difference will be the result when subtraction is the last operation applied in the order of operations for the expression. this means subtraction must be outside of the parenthesis. only b has this.