Expand binomial expressions (a + b)^n using the binomial theorem with detailed steps
Enter the coefficients a, b and exponent n to expand (a + b)^n
Binomial Theorem
(a + b)^n = ∑ C(n,k) a^(n-k) b^k (for k from 0 to n)
C(n,k) Formula
C(n,k) = n! / (k! × (n-k)!)
(a + b)^n = ∑ C(n,k) a^(n-k) b^k (k=0 to n)
Where: C(n,k) = binomial coefficient, n = exponent, k = term index
Our Binomial Expansion Calculator helps you expand expressions of the form (a + b)^n using the binomial theorem. This powerful algebraic tool provides step-by-step solutions for expanding binomial expressions, making complex calculations accessible and educational.
The binomial theorem describes the algebraic expansion of powers of a binomial. It states that any positive integer power of a binomial can be expanded into a sum of terms involving binomial coefficients.
(a + b)^n = C(n,0) a^n b^0 + C(n,1) a^(n-1) b^1 + C(n,2) a^(n-2) b^2 + ... + C(n,n) a^0 b^n
Binomial coefficients C(n,k) represent the number of ways to choose k elements from a set of n elements. They form Pascal's triangle and can be calculated using the formula:
C(n,k) = n! / (k! × (n-k)!)
For example, C(5,2) = 5! / (2! × 3!) = 120 / (2 × 6) = 10.
Example 1: (x + y)^2
Expansion: x² + 2xy + y²
(x + y)² = C(2,0) x² y⁰ + C(2,1) x¹ y¹ + C(2,2) x⁰ y² = 1·x² + 2·xy + 1·y²
Example 2: (2x - 3)^3
Expansion: 8x³ - 36x² + 54x - 27
(2x - 3)³ = C(3,0) (2x)³ (-3)⁰ + C(3,1) (2x)² (-3)¹ + C(3,2) (2x)¹ (-3)² + C(3,3) (2x)⁰ (-3)³
Example 3: (a + b)^4
Expansion: a⁴ + 4a³b + 6a²b² + 4ab³ + b⁴
Following the pattern of binomial coefficients: 1, 4, 6, 4, 1
Q1. What is the binomial theorem?
A: The binomial theorem provides a formula for expanding expressions of the form (a + b)^n into a sum of terms.
Q2. How do binomial coefficients work?
A: Binomial coefficients C(n,k) count the number of ways to choose k items from n items and appear in Pascal's triangle.
Q3. Can I expand expressions with negative exponents?
A: This calculator handles positive integer exponents. For negative exponents, use the binomial series expansion.
Q4. What is Pascal's triangle?
A: Pascal's triangle is a triangular array of binomial coefficients where each number is the sum of the two numbers above it.
Q5. How is this used in probability?
A: The binomial theorem forms the basis of the binomial probability distribution, used for modeling success/failure experiments.
For further understanding and validation of the formulas used above, we recommend exploring these authoritative resources: