Free graphing resources · Original practice
Graphing square root functions.
Start at the endpoint.
Plot four one-sided radical curves from y=a√(x-h)+k. Locate the endpoint, complete perfect-square samples and compare reflected and shifted roots.
4 square-root cases.
Endpoint + smooth curve.
More ways to practice
A new worked example with independent checks
Consider y = -2√(x - 1) + 3. The expression under the root must be nonnegative, so x - 1 ≥ 0, giving domain x ≥ 1. The endpoint occurs when the radicand is zero: x = 1, and then y = -2√0 + 3 = 3. Plot the endpoint at (1, 3) with a solid dot because the domain includes x = 1.
Choose perfect-square offsets to keep arithmetic simple. Let x - 1 = 1, so x = 2 and y = -2(1) + 3 = 1. Let x - 1 = 4, so x = 5 and y = -2(2) + 3 = -1. Let x - 1 = 9, so x = 10 and y = -2(3) + 3 = -3. These points (2, 1), (5, -1), and (10, -3) lie on the curve. Because a = -2 is negative, the curve opens downward from the endpoint; because |a| = 2, it rises or falls twice as fast as the parent square root curve.
- State the domain by solving the inequality inside the square root: x - 1 ≥ 0, so x ≥ 1.
- Find the endpoint by setting the radicand to zero: x = 1, y = 3; mark it as a solid point.
- Substitute perfect-square offsets 1, 4, and 9 into x - 1 to get x = 2, 5, and 10.
- Compute the corresponding y-values: 1, -1, and -3.
- Plot the four points and draw a smooth one-sided curve that starts at the endpoint and moves downward to the right.
- Check one plotted point by substituting its coordinates into the original equation.
Diagnostic checks for endpoint, domain and reflection
A frequent error is plotting the endpoint at the wrong x-value. For y = a√(x - h) + k, the endpoint is always at x = h, not at x = 0 unless h = 0. If your graph starts at the origin for a shifted function, recheck the horizontal shift. Another error is drawing a two-sided curve; the square root function has only one side because the domain is restricted to x ≥ h when a is real.
Reflection is controlled by the sign of a. If a is positive, the curve extends upward from the endpoint; if a is negative, it extends downward. A common mistake is to reflect the curve but keep the endpoint in the same place without checking that the endpoint is still on the curve. The endpoint is always on the curve because the radicand is zero there, so y = k. Verify that your endpoint has y-coordinate k.
Steepness is controlled by |a|. For |a| > 1, the curve is steeper than the parent; for 0 < |a| < 1, it is flatter. Do not confuse a vertical stretch with a horizontal shift. A quick check is to compare the y-value at one perfect-square offset with the parent value multiplied by a.
- Confirm the endpoint x-coordinate equals h and the y-coordinate equals k.
- Check that the domain inequality matches the direction of the curve: x ≥ h means the curve exists only to the right of the endpoint.
- Verify the sign of a by checking whether the curve goes up or down from the endpoint.
- Substitute one non-endpoint point into the equation to confirm it satisfies the function.
- Ensure the curve is smooth and one-sided, not a full parabola or a two-sided radical shape.
Practical variation: comparing two functions on one grid
To deepen understanding, graph y = √(x - 2) and y = -√(x - 2) + 4 on the same coordinate grid. The first has endpoint (2, 0) and opens upward; the second has endpoint (2, 4) and opens downward. Use perfect-square offsets 1, 4, and 9 to generate points for each. For the first, points include (3, 1), (6, 2), and (11, 3). For the second, points include (3, 3), (6, 2), and (11, 1). Notice that the second curve is the first curve reflected across a horizontal line and shifted, but you can verify each point independently.
This comparison helps distinguish horizontal shifts from vertical shifts and reflections. Label each curve clearly and mark endpoints with solid dots. Use a ruler for axes and keep equal spacing on both axes so steepness comparisons are meaningful.
- Draw axes with equal unit spacing and label them x and y.
- Plot the endpoint of each function: (2, 0) and (2, 4).
- Generate three perfect-square sample points for each function using offsets 1, 4, and 9.
- Plot the points and draw smooth one-sided curves.
- Check that each curve starts at its endpoint and extends only to the right.
Try this example
Graph y = 3√(x + 2) - 1 and verify three points.
Show the worked explanation
Domain: x + 2 ≥ 0, so x ≥ -2. Endpoint: set x + 2 = 0, so x = -2 and y = 3√0 - 1 = -1; endpoint (-2, -1). Choose offsets 1, 4, and 9: x + 2 = 1 gives x = -1, y = 3(1) - 1 = 2; x + 2 = 4 gives x = 2, y = 3(2) - 1 = 5; x + 2 = 9 gives x = 7, y = 3(3) - 1 = 8. Points: (-1, 2), (2, 5), (7, 8). Check (2, 5): 3√(2 + 2) - 1 = 3√4 - 1 = 3(2) - 1 = 5, correct. The curve starts at (-2, -1) and rises to the right because a = 3 is positive.
Common mistakes
- Plotting the endpoint at x = 0 for a function with a horizontal shift, such as y = √(x - 3). Set the radicand to zero: x - 3 = 0 gives x = 3. The endpoint is at (3, 0), not the origin.
- Drawing a two-sided curve that extends left of the endpoint. State the domain first. For y = a√(x - h) + k with real a, the domain is x ≥ h, so the graph exists only to the right of the endpoint.
- Reflecting the curve but leaving the endpoint at the wrong y-value. The endpoint y-coordinate is always k. For y = -√(x - 1) + 5, the endpoint is (1, 5), regardless of the reflection.
Check your work
- Endpoint is correctly identified and plotted with a solid dot at (h, k).
- Domain is stated as x ≥ h and the curve is drawn only on that side.
- At least three sample points are generated using perfect-square offsets and plotted accurately.
- The sign of a correctly determines whether the curve rises or falls from the endpoint.
- The steepness of the curve reflects the value of |a| compared with the parent square root curve.
- Axes are labeled, scale is uniform, and the curve is smooth and one-sided.
Questions before you start
How do I find the endpoint of a square root function graph?
Set the expression inside the square root equal to zero and solve for x. That x-value is the endpoint's x-coordinate. Substitute it into the function to find the y-coordinate, which will equal k in y = a√(x - h) + k.
Why does a square root function graph only go in one direction?
The principal square root is defined only for nonnegative radicands. For y = a√(x - h) + k, this means x - h ≥ 0, so x ≥ h. The graph therefore exists only on one side of the endpoint.
How can I check whether my plotted square root curve is correct?
Substitute the coordinates of at least two plotted points into the original equation. Confirm the endpoint satisfies the equation, the domain matches the direction of the curve, and the sign of a matches whether the curve rises or falls from the endpoint.