What is the range of the function \(f(x)=x^2+4\)?

Correct answer: \([4,\infty)\)

For every real \(x\), \(x^2\ge 0\), so \(f(x)=x^2+4\ge 4\). At \(x=0\), \(f(0)=4\), so 4 is included in the range. Therefore, the range is \([4,\infty)\). Option B is the range of \(x^2\) before adding 4, while option C incorrectly excludes the endpoint 4. Exam tip: For a quadratic involving a square, first identify its minimum value.