Multiplying Radicals - Same and Different Index Solver
Use this multiplying radicals calculator to combine nth roots with matching or different indices, pull out perfect-power factors, and read the simplified radical form.
Multiplying Radicals
Results
What Is Multiplying Radicals?
A multiplying radicals calculator is a math tool that multiplies two radicals (nth roots) and reports the result in symbolic and numeric form. It applies the same-index product rule (n√a × n√b = n√(a × b)) when the indices match, and rewrites the product with the LCM of the indices when they do not, so the result is always in simplest radical form.
- • Simplify an algebra homework expression: Combine two square roots or nth roots from a chapter problem into a single simplified radical so the answer matches the textbook key.
- • Check a math test answer: Plug in a student's by-hand result to confirm the indices, the combined radicand, and the integer pulled out by simplification before grading.
- • Compare a radical product with a fractional-exponent form: Convert the same product into a base raised to a fraction so it can be read side by side with a fractional-exponent answer key.
- • Mix square and cube roots in one expression: Multiply a square root and a cube root of the same base, get the LCM-index form (usually the sixth root) and read the simplified result.
The calculator accepts real radicands and positive integer indices. A negative radicand is only allowed with an odd index because the even-index root of a negative is not a real number. When a radicand is 0, the product is 0 in every case, so the calculator short-circuits and reports 0 as the simplified form.
When the same product is more naturally written as a^m times a^n, the multiplying exponents calculator applies the same-base product rule so the symbolic and numeric answers stay in step with this tool.
How Multiplying Radicals Works
The calculator reads a, m, b, and n, validates the inputs, and chooses one of three branches: same-index product, same-index product with simplification, or different-index product with the LCM of the two indices.
- a, b (radicands): The numbers under the first and second radical. Any real number is allowed, but a negative radicand only returns a real result when its index is odd.
- m, n (indices): The degrees of the two roots. 2 means square root, 3 means cube root, 4 means fourth root, and so on. Both must be positive integers.
- LCM(m, n) (combined index): The least common multiple of the two indices, used when they do not match. Each radicand is raised to the LCM divided by its own index so the two fractional exponents collapse into a single radical.
- Symbolic form: The simplified product. The integer pulled out by simplification is shown in front of the radical; the leftover radicand is shown inside.
The numeric product is computed with Math.pow so it agrees with the symbolic form to four significant figures. When the indices differ, the calculator also returns the LCM of the two indices so it is easy to see why the combined form uses a specific root (for example, LCM(2,3) = 6 means the combined result is a sixth root).
Worked example: √8 × √2 that simplifies to 4
a = 8, m = 2, b = 2, n = 2
8 × 2 = 16, a perfect square, so √16 = 4 and the radical collapses to a plain number.
4
The same-index rule gives √16 first, then the simplification pass pulls 4 out and leaves the combined index at 1. The numeric product 4.0000 matches the symbolic form exactly.
According to Math is Fun, a radical with index n is the same as raising the radicand to the power 1/n, and multiplying two radicals with the same index is done by multiplying the radicands and keeping the index unchanged.
Because every radical is also a base raised to a reciprocal index, the fractional exponent calculator is the natural cross-check whenever the product of two radicals is easier to read as a single base raised to a fraction.
Key Concepts Explained
Four concepts cover every step the calculator takes, and they are the same ideas an algebra textbook uses when it teaches how to multiply radicals.
Same-index product rule
When the two radicals share the same index, the product is one radical of the product of the radicands: n√a × n√b = n√(a × b). The index stays put, the radicands multiply, and the simplification pass runs on the result.
Different-index LCM form
When the two indices differ, find the LCM of the indices and rewrite each radicand raised to the LCM divided by its own index. The product becomes one radical of a combined radicand, which is the form an algebra teacher expects when a square root and a cube root appear in the same expression.
Pulling out perfect nth powers
After the radicands are combined, the calculator scans for the largest integer that, raised to the index, divides the combined radicand. That integer is moved in front of the radical as a multiplier, leaving a smaller radicand behind.
Radicals as fractional exponents
The nth root of a is the same as a^(1/n), so multiplying radicals is the same problem as adding fractional exponents with a common denominator.
After the combined radicand is reduced to an integer times a radical, the leftover integer coefficient behaves like a fraction coefficient, and the multiplying fractions calculator is the right next stop when the product of the coefficients needs the same simplification pass.
How to Use This Calculator
The form takes the first radical as a and m, and the second as b and n. The result panel updates as soon as any field changes.
- 1 Enter the first radicand: Type the number under the first radical into the a field. Negative values are only valid when the matching index is odd.
- 2 Enter the first index: Type the first index into the m field. 2 means square root, 3 means cube root, and so on. Index values must be positive integers; 1 is rejected because it is the identity, not a root.
- 3 Enter the second radicand: Type the number under the second radical into the b field. The calculator multiplies the radicands directly when the indices match.
- 4 Enter the second index: Type the second index into the n field. When m and n differ, the calculator computes the LCM of the two indices for the combined radical form.
- 5 Read the simplified form and the rule: The Simplified radical form field shows the result in simplest radical form and the Rule applied field names the branch used.
- 6 Cross-check the numeric product: The Numeric product field shows the decimal value to four significant figures, which is a fast way to confirm the symbolic form is right.
A homework problem asks for √8 × √2. Enter a = 8, m = 2, b = 2, n = 2. The simplified form is 4 and the rule label reads same-index simplified.
When the original problem wraps the radicals inside a polynomial product such as (a + √b)(c + √d), the multiplying polynomials calculator handles the binomial expansion and the result feeds back into this tool for the radical-by-radical step.
Benefits of Using This Calculator
The result gives you the simplified radical form, the combined index, the numeric product, and the rule label, so a single read covers everything a teacher or a textbook answer would check.
- • Handles same-index and different-index products in one tool: The same form works for two square roots, two cube roots, or a mix of square and cube roots. The calculator picks the right rule and the right combined index, so the user does not have to switch tools for mixed problems.
- • Simplifies the combined radicand automatically: Perfect nth-power factors are pulled out as an integer in front of the radical, so the answer is in the same simplified radical form that an algebra key uses. Expressions like √8 × √2 collapse to 4 in a single step.
- • Labels the rule that was used: The Rule applied field names the branch the calculator used, so a student can see whether the same-index product rule or the different-index LCM rule was applied.
- • Cross-checks the symbolic form with a numeric product: The decimal value is computed separately using the fractional-exponent form, so the symbolic answer and the numeric answer agree to four significant figures.
- • Rejects combinations that are not real numbers: Negative radicands with an even index, and index values of 1 or non-integer entries, surface a clear validation message instead of returning a fake number.
Once the simplified radical form is in hand, the simplify fractions calculator runs the same factor-out-and-reduce pass on the leftover integer coefficient so it lands next to the radical in lowest terms.
Factors That Affect Your Results
A few characteristics of the input change which rule the calculator chooses and how the simplified form is written.
Whether the indices match
When m and n are equal, the same-index product rule applies and the result is one radical of the product of the radicands. When they differ, the calculator rewrites the product with the LCM of the two indices, so the combined radical is at index LCM(m, n).
Whether the combined radicand has a perfect nth power
If the combined radicand is a perfect nth power (or has a perfect nth-power factor), the simplification pass pulls the integer root out in front of the radical. This is what turns √8 × √2 into 4.
Whether the radicand is negative and the index is even or odd
A negative radicand is only a real number when its index is odd, so even-index roots of a negative are rejected. The product of two negative radicands is positive, which the calculator handles by tracking the sign separately from the magnitude.
Magnitude of the indices and radicands
Large indices make the LCM grow quickly, and large radicands make the integer pulled out by simplification grow quickly. Both stay readable because the calculator keeps the symbolic form in plain text.
- • The calculator handles two radicals at a time. For three or more, run it on the first two, treat the simplified result as a new single radical, and feed it back in with the third.
- • Negative radicands are only allowed with odd indices, because even-index roots of a negative are not real numbers. The calculator surfaces a validation error instead of returning an imaginary result.
According to Wikipedia Nth root, the product of two n-th roots with the same index is the n-th root of the product of the radicands, and roots with different indices can be rewritten with a common index equal to the least common multiple of the original indices.
According to Khan Academy, multiplying radicals is the same as multiplying the radicands when the indices match, and the result can be simplified by pulling out perfect-square or perfect-nth factors from the combined radicand.
When the combined radicand shares a factor with the index, the simplification pass works the same way the factoring trinomials calculator pulls a common term out of a quadratic, so the leftover radicand sits at its smallest integer base.
Frequently Asked Questions
Q: How do you multiply two radicals with the same index?
A: Keep the index and multiply the radicands. For example, √2 × √3 = √6, and ³√4 × ³√5 = ³√20. After the multiplication, scan the combined radicand for perfect nth-power factors and pull them out in front of the radical.
Q: How do you multiply radicals with different indices?
A: Find the LCM of the two indices and rewrite each radical under that combined index. For a square root and a cube root the LCM is 6, so √4 × ³√4 becomes the sixth root of 4^5.
Q: What is the rule for multiplying square roots?
A: For square roots the index is 2, so the rule simplifies to √a × √b = √(a × b). For example, √5 × √7 = √35, and √12 × √3 = √36 = 6 once the perfect square 36 is pulled out.
Q: Can you multiply a radical by a non-radical number?
A: Yes. Write the non-radical as a radical of index 1, which is just the number itself. For example, 3 × √2 = 3√2, and 2 × ³√9 = 2³√9 unless 9 has a perfect cube factor.
Q: How do you simplify radicals after multiplying?
A: Look for the largest integer that, raised to the index, divides the combined radicand. Move that integer in front of the radical. For example, √8 × √2 = √16 = 4, and ³√16 × ³√4 = ³√64 = 4.
Q: How do you multiply radicals with variables?
A: Treat the variable the same way you would a number. For example, √x × √x = √(x ²) = x (for non-negative x), and ³√x × ³√x × ³√x = ³√(x^3) = x.