UNIT 01 – LESSON 11 – ALGEBRAIC PROOFS ESSENTIAL QUESTION How can algebraic properties help you solve an equation? SCHOLARS WILL… Use algebra to write two-column proofs Use properties of equality to write geometric proofs.
WHAT IS AN ALGEBRAIC PROOF? An algebraic proof is a proof is a proof that is made up of a series of algebraic statements. The properties of equality provide justification for many statements in algebraic proofs.
ALGEBRAIC PROPERTIES OF EQUALITY (CARD #12)
HOW DO YOU JUSTIFY EACH STEP WHEN SOLVING EQUATIONS? Algebraic StepsProperties 2(5 – 3a) – 4(a + 7)=92Original equation 10 – 6a – 4a – 28=92Distributive Property –18 – 10a=92Substitution Property –18 – 10a + 18 = Addition Property –10a=110 Substitution Property a=–11 Substitution Property
HOW DO YOU JUSTIFY EACH STEP WHEN SOLVING EQUATIONS? Solve –3(a + 3) + 5(3 – a) = –50. Justify each step.
HOW DO YOU WRITE AN ALGEBRAIC PROOF?
Begin by stating what is given and what you are to prove. 2. d – 5 = 20t2. Addition Property of Equality StatementsReasons Proof: 1. Given 1. d = 20t Symmetric Property of Equality 3.3. Division Property of Equality = t
HOW DO YOU WRITE A GEOMETRIC PROOF? If A B, m B = 2m C, and m C = 45, then m A = 90. Write a two-column proof to verify this conjecture.
5. m A = Substitution StatementsReasons Proof: 4. Substitution 4. m A = 2(45) 2. m A = m B 2. Definition of angles 1. Given 1. A B; m B = 2m C; m C = Transitive Property of Equality 3. m A = 2m C
TRY ON YOUR OWN: If the formula for the area of a trapezoid is, then the height h of the trapezoid is given by.