Add binomial_expansion function building on binomial_coefficient

- Computes (a + b)^n for both positive and negative integer exponents
- Uses existing binomial_coefficient function for term computation
- Raises ZeroDivisionError when base is 0 and exponent is negative
- Includes doctests and example cases

Author: aditya7balotra

maths/binomial_expansion.py

@@ -0,0 +1,52 @@
+from maths.binomial_coefficient import binomial_coefficient
+
+
+def binomial_expansion(a: float, b: float, n: int) -> int | float:
+    """
+    Compute the value of (a + b)^n using the Binomial Theorem.
+
+    This function works for both positive and negative integer exponents.
+    It raises a ZeroDivisionError if the base (a + b) is 0 and n is negative.
+
+    Args:
+        a: First term (int or float).
+        b: Second term (int or float).
+        n: Exponent (must be integer).
+
+    Returns:
+        The result of the binomial expansion (a + b)^n.
+
+    Raises:
+        ZeroDivisionError: If a + b == 0 and n < 0.
+
+    Examples:
+        >>> binomial_expansion(2, 3, 2)
+        25
+        >>> binomial_expansion(100, -4, 3)
+        884736
+        >>> binomial_expansion(2, 2, -2)
+        0.0625
+        >>> binomial_expansion(0, 0, 3)
+        0
+        >>> binomial_expansion(-2, 2, -1)
+        Traceback (most recent call last):
+            ...
+        ZeroDivisionError: Cannot raise 0 to the negative power
+    """
+    total = a + b
+    if total == 0 and n < 0:
+        raise ZeroDivisionError("Cannot raise 0 to the negative power")
+
+    abs_n = abs(n)
+    value = sum(
+        binomial_coefficient(abs_n, i) * (a ** (abs_n - i)) * (b**i)
+        for i in range(abs_n + 1)
+    )
+
+    return value if n >= 0 else 1 / value
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()