Assuming that the domain of the given function is R meaning that x takes all values in the interval (−∞,+∞) which means that x2 is either zero or positive. Hence we can write the following inequality
x2≤0
Add 5 to both sides of the inequality to obtain the inequality
x2+5≤=0+5orf(x)≤5
The range of f(x)=x2+5 is given by the interval: [5,+∞)