SECONDARY ALGEBRA
posted by Grace .
A rectangular field is to be fenced off with 120 m of fencing materials. the length of the field is x. express the area in square meters of the field as a function of x.

f(x)=(120m^3)x

nice try, but you're mixing things up. Why do you say 120 m^3? m^3 is volume, not are or length! And why multiply the perimeter by the length, anyway?
Just take a step back and work things out.
The area is length * width
The 120m of fencing reaches around the field  that is the perimeter.
If the perimeter is 120, that means that
2(length+width)=120
length+width=60
So, if the length is x,
width = 60x
That means that the area is
x(60x)
and that is in m^2: meters * meters