Brahmagupta–Fibonacci identity

Target entity: Brahmagupta–Fibonacci identity
Context triple: [Indian mathematics, hasNotableConcept, Brahmagupta–Fibonacci identity]

• A. Fermat's theorem on sums of two squares
  Fermat's theorem on sums of two squares is a result in number theory stating exactly which prime numbers (and, more generally, which integers) can be expressed as the sum of two perfect squares.
• B. Lagrange's four-square theorem
  Lagrange's four-square theorem is a fundamental result in number theory stating that every natural number can be expressed as the sum of four integer squares.
• C. Legendre's three-square theorem
  Legendre's three-square theorem is a result in number theory that characterizes exactly which positive integers can be expressed as the sum of three squares of integers.
• D. Ramanujan–Nagell equation
  The Ramanujan–Nagell equation is a famous Diophantine equation in number theory that has only finitely many integer solutions and is closely associated with the work of Srinivasa Ramanujan.
• E. Jacobi’s four-square theorem
  Jacobi’s four-square theorem is a fundamental result in number theory that gives a precise formula for the number of ways an integer can be expressed as a sum of four squares.
• F. None of above. chosen
• G. Unsure - the case is ambiguous/there is not enough information to decide.

Target entity: Brahmagupta–Fibonacci identity
Target entity description: The Brahmagupta–Fibonacci identity is a classical algebraic formula showing that the product of two sums of two squares can itself be expressed as a sum of two squares, fundamental in number theory and the study of quadratic forms.

• A. Fermat's theorem on sums of two squares
  Fermat's theorem on sums of two squares is a result in number theory stating exactly which prime numbers (and, more generally, which integers) can be expressed as the sum of two perfect squares.
• B. Lagrange's four-square theorem
  Lagrange's four-square theorem is a fundamental result in number theory stating that every natural number can be expressed as the sum of four integer squares.
• C. chakravala method for solving indeterminate equations
  The chakravala method for solving indeterminate equations is an ancient Indian cyclic algorithm, notably used to solve Pell-type quadratic Diophantine equations with remarkable efficiency and generality.
• D. Legendre's three-square theorem
  Legendre's three-square theorem is a result in number theory that characterizes exactly which positive integers can be expressed as the sum of three squares of integers.
• E. Ramanujan–Nagell equation
  The Ramanujan–Nagell equation is a famous Diophantine equation in number theory that has only finitely many integer solutions and is closely associated with the work of Srinivasa Ramanujan.
• F. None of above. chosen