Math calculator

Binomial Expansion Calculator

Expand (ax+b)ⁿ into descending powers of x for a nonnegative integer exponent. The displayed expanded polynomial includes enough working to inspect signs and scale.

Binomial Expansion inputs

Numerical setup

Reading the calculation

The binomial theorem writes (ax+b)ⁿ as a sum of C(n,k)(ax)ⁿ⁻ᵏbᵏ. Pascal’s row provides the combinatorial coefficients.

A correct expanded polynomial therefore depends on choosing the model before entering the numbers.

Where this calculation appears

Expansion connects factored and polynomial forms, supports coefficient questions, and makes derivatives or evaluations easier in some contexts.

Reading the Binomial Expansion result

The exponent must be a manageable nonnegative integer. Signs from a negative b alternate by the power of b, and zero coefficients can remove terms. If the Binomial Expansion assumptions do not fit, consider coefficient row.

Carry the available precision through binomial expansion, then round the final output rather than its intermediate parts.

Example from start to finish

For (2x−3)⁴, the coefficients are 16,−96,216,−216,81, giving 16x⁴−96x³+216x²−216x+81.

Manual method

Read row n of Pascal’s triangle, multiply each entry by aⁿ⁻ᵏbᵏ, and attach xⁿ⁻ᵏ before combining signs. Binomial Expansion also leads to check a value.

What changes—and what does not

Write each source value under its matching label before calculating: coefficient a, constant b and exponent n. This preserves the assumptions behind expanded polynomial and makes a later check possible without reopening the original problem.

How the output responds

Changing b changes each term according to a different power; changing n alters both the number of terms and the coefficient row. This relationship remains useful even when the final expanded polynomial is rounded.

Precision and reporting

Before publishing or sharing expanded polynomial, decide on units, significant digits, and whether an exact form is expected. Those choices belong to interpretation rather than the calculator engine.

Pascal’s triangle supplies coefficients only, while this page also applies a, b, signs, and powers of x. The two results may share inputs while retaining different meanings.

When reporting the answer, state the expanded polynomial first, then its value and unit. Add coefficient a, constant b and exponent n if someone else must verify the work independently.

Saving a defensible Binomial Expansion result

Store Coefficient a, Constant b, Exponent n with the Binomial Expansion output and identify the event in words. Inputs alone may not reveal whether odds were for or against, whether a row began at zero, or whether a cumulative boundary was inclusive. A short convention note prevents a correct value from being attached to the wrong question.

For Binomial Expansion, before saving, check one invariant appropriate to the page: an integer count stays whole, a probability remains bounded, complementary areas total one, or a union does not exceed the summed set sizes.

Questions about Binomial Expansion

How many terms appear?

Normally n+1 before zero coefficients are removed.

Why can signs alternate?

Odd powers preserve a negative b.

Can n be zero?

Yes; every nonzero base to power zero gives 1.

How do I verify the expansion?

Evaluate both forms at the same simple x value.