Need to find the domain of f(x) = (840 - 2x) * xI came up with (-inf, inf) and that was an incorrect answer.

[0.5/1 Points] DETAILS PREVIOUS ANSWERS MY A rectangular field is to be enclosed by 840 feet of fence. One side of the field is a building, so fencing is not required on that side. Fenced Area Building If x denotes the length of one side of the rectangle perpendicular to the building, determine the function in the variable x giving the area (in square feet) of the fenced-in reg Area, as a function of x - (840 - 2x ) . x Determine the domain of the area function, Enter your answer using interval notation. 839 Domain of area function 2 X Submit Answer 7. [-/1 Points] DETAILS