Final answer:
Without more context, it's impossible to determine the value of EG, though it may be a variable in an algebraic or geometric problem that can be solved through equations.
Step-by-step explanation:
To determine what EG is, we need more context, as the expression for EG could represent a variety of mathematical relationships depending on the specific problem or concept being discussed. It seems as though the expressions given (y^2, x + y, 2y - x) might be options provided for the value of EG in a particular geometric or algebraic context. Within the context of the additional information provided, it appears that there is a discussion about solving equations, graphing functions, and analyzing the trajectory of parabolas, implying that we are working with algebra and possibly coordinate geometry.
Without additional information, we cannot confidently provide the correct value for EG. However, if one had two equations and EG were a variable representing a specific geometric length or algebraic quantity, one would typically solve for EG by setting the equations equal to each other where one of them may contain EG as a variable. The algebra often involves isolating the variable on one side of the equation and solving for its value using algebraic manipulation and substitution.