Domain: (-∞, ∞), since f(x) is defined for all real values of x.
Range: [7, ∞), since the minimum value of f(x) is 7, and f(x) is open up, there is no upper limit.
The domain is negative infinity to positive infinity. The factor of x is the numerator, not the divisor. Therefore, it can be zero. It is also not being square-rooted. Therefore, it can be a negative number.
The range is different because x2 will render any value of x either zero or a positive number. We need to establish the minimum while recognizing there is no maximum.