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Mathovia

Math Practice

Domain and Range Practice Problems

Fifteen hand-built problems on domain and range, each fully worked. The domain half drills the three restrictions — a zero denominator, an even root of a negative, and a logarithm — while the range half works from the shape of the function, including a quadratic capped at its vertex and a restricted domain with a turning point inside it.

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Domain and Range Practice Problems

Two lessons feed this set: Domain and Range. They are practised together because exam questions almost always ask for both off the same function, and the contrast is what makes each one stick.

How to use this set

The two halves work differently, and it is worth being conscious of which one you are doing.

Domain is subtractive: start from all real numbers and remove what breaks — a zero denominator, a negative under an even root, a non-positive logarithm argument.

Range is constructive: think about what the expression can actually produce. A square is never negative, a square root is never negative, and a parabola is capped at its vertex.

Answers go in interval notation. Every equivalent spelling is accepted, but the bracket type is checked, since that is the distinction being taught.

Common mistakes to watch for

Excluding zeros of the numerator. Only the denominator restricts the domain.

Restricting an odd root. Cube roots accept negatives.

Forgetting to flip the inequality when dividing by a negative: gives .

Assuming a root in a denominator still allows zero. It does not — that tightens into .

Copying the domain as the range. They are usually different intervals.

Using only the endpoints on a restricted domain. Check for a turning point inside it.

Where to go next

Interval Notation drills the bracket conventions on their own. Function Notation is the evaluation skill underneath, and Function Operations asks for domains of combined and composed functions.

Frequently Asked Questions

What is the difference between domain and range?+

Domain is the set of allowed inputs, read horizontally as the graph's shadow on the -axis. Range is the set of produced outputs, read vertically on the -axis.

What are the three things that restrict a domain?+

A denominator that could be zero, an even root of a negative number, and the argument of a logarithm being zero or negative. Start from all real numbers and remove only what genuinely fails.

Why is a square root's bracket square but a logarithm's round?+

is defined, so zero is included and the bracket is square. is undefined, so zero is excluded and the bracket is round.

Why is the range harder to find than the domain?+

The domain comes from ruling out a short list of broken operations. The range depends on the overall shape — where the turning points are and how the function behaves at its extremes — so a sketch is usually the fastest route.

How do I find the range on a restricted domain?+

Check whether a turning point lies inside the interval. If it does, it supplies the maximum or minimum; if not, the two endpoints do. Evaluating only the endpoints is the classic trap.

How should I type interval answers?+

Any equivalent spelling is accepted — `[-6, inf)`, `[-6, ∞)`, or the inequality `x >= -6`. The bracket type matters though, because that is what the exercise is testing. Use `U` or `∪` for a union.

More practice problems