Let \(f(x)=\sqrt{4x+1}-2\).
1. Find the maximal real domain of \(f\).
2. Determine which points lie on the graph of \(f\): \(A(0, -1)\), \(B(2, 1)\), \(C(-1, -1)\), \(D(0.75, 0)\), and \(E(6, 3)\).
Hints
- Require the expression under the square root to be nonnegative.
- For each point, substitute its x-coordinate and compare the result with its y-coordinate.
- Check the domain before evaluating a point.
Solution
1. The radicand must be nonnegative: \(4x+1\ge0\), so \(x\ge-0.25\). The domain is \([-0.25, \infty)\).
2. For A, \(f(0)=\sqrt{1}-2=-1\), so A is on the graph.
3. For B, \(f(2)=\sqrt{9}-2=1\), so B is on the graph.
4. Point C is not on the graph because \(-1\) is outside the domain.
5. For D, \(f(0.75)=\sqrt{4}-2=0\), so D is on the graph.
6. For E, \(f(6)=\sqrt{25}-2=3\), so E is on the graph.
Answer
1. \([-0.25, \infty)\)
2. Points A, B, D, and E lie on the graph. Point C does not.