Algebra is a branch of mathematics that substitutes letters for numbers. Important Formulas in Algebra Here is a list of Algebraic formulas – a 2 – b 2 = (a – b)(a + b) (a + b) 2 = a 2 + 2ab + b 2 a 2 + b 2 = (a + b) 2 – 2ab (a – b) 2 = a 2 – 2ab + b 2 (a + b + c) 2 = a 2 + b 2 + c 2 + 2ab + 2bc + 2ca (a – b – c) 2 = a 2 + b 2 + c 2 – 2ab + 2bc – 2ca (a + b) 3 = a 3 + 3a 2 b + 3ab 2 + b 3 ; (a + b) 3 = a 3 + b 3 + 3ab(a + b) (a – b) 3 = a 3 – 3a 2 b + 3ab 2 – b 3 = a 3 – b 3 – 3ab(a – b) a 3 – b 3 = (a – b)(a 2 + ab + b 2 ) a 3 + b 3 = (a + b)(a 2 – ab + b 2 )