2.5 Reasoning and Algebra
Addition Property If A = B then A + C = B + C
Subtraction Property If A = B then A – C = B - C
Multiplication Property If A = B then AC = BC
Division Property If A = B and C is not 0 then A/C = B/C Why cant C = 0?
Substitution Property If A = B then A can be substituted for B in any equation
Distributive property A(B + C) = AB + AC
Reflexive Property For real numbers: A= A For Segments AB = AB For angles m<A = m<A
Symmetric Property For real numbers: if A = B then B = A For segments: if AB = CD then CD = AB For angles: If m<A = m<B then m<B = m<A
Transitive Property For real numbers: If A = B and B = C then A = C For Segments: if AB = BC and BC = CD then AB = CD For angles: if m<A = m<B and m<C = m<D then m<A = m<C
Proofs This is an explanation of what you are doing to solve a problem or prove a theory You use the rules you know to do this
2 Column Proof
Proofs
2x + 15 = 3x = x = x X = 5 Given Subtraction Symmetric
5X – 9 = 3X + 1 2X – 9 = 1 2X = 10 X = 5 Given Subtraction Addition Division
2(X – 5) = 3X + ½ 2X – 10 = 3X + ½ -10 = X + ½ -20 = 2X = 2X = X X = Given Distributive Subtraction Multiplication Subtraction Division Symmetric