Domain: Possible x values
There's nothing like a fraction bar or square root or anything that mean certain values of x can't be used.
The domain is all real numbers.
Range: Possible f(x) values
There's an x^2. Those are always positive.
As x becomes very small (close to 0), 1/(x^2) becomes very large, blowing up to + infinity.
As x becomes very large (either + infinity or - infinity), 1/(x^2) approaches 0, but never becomes negative. The limit as x goes to infinity (+ or -) of 1/(x^2) is 0. The smallest f(x) can be is 5/2.
The range is 5/2 to infinity.