For this case we have that by definition, a function is of the form:
So, we have the following system of equations:
Equating the equations we have:
Adding 2x to both sides of the equation:
Subtracting 2 from both sides of the equation:
Dividing between -4 on both sides of the equation:
Thus, the value of the variable "x" is -0.5.
Answer:
-0.5