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SECTION 2-6. Algebraic Proofs. JIM SMITH JCHS. Properties we’ll be needing. REFLEXIVE -- a=a SYMMETRIC -- if x=2 then 2=x TRANSITIVE -- if a=b and b=c then a=c SUBSTITUTION -- If a=b then a may be used in any equation instead of b. DISTRIBUTIVE -- a(b+c) = ab+ac
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SECTION2-6 Algebraic Proofs JIM SMITH JCHS
Properties we’ll be needing • REFLEXIVE -- a=a • SYMMETRIC -- if x=2 then 2=x • TRANSITIVE -- if a=b and b=c then a=c • SUBSTITUTION -- If a=b then a may be used in any equation instead of b
DISTRIBUTIVE -- a(b+c) = ab+ac • ADD and SUBTRACT -- if a=b then a+c=b+c and a-c=b-c • MULT and DIVIDE – if a=b then ac=bc and a/c = b/c
2 COLUMN PROOFS Statements Reasons
In an algebraic proof, you must show all steps used to solve the equation. Each individual step you use is a statement in the proof. You then give each statement a reason.
SHOW ME - THEN DO IT • WHEN WE ADD, SUBTRACT, MULT, OR DIV BOTH SIDES OF THE EQUATION, SHOW ME WHAT YOU ARE GOING TO DO FIRST • THE NEXT STEP IS THE DO IT STEP
Given: 2x+5=17Prove x=6 Start by stating the given. The reason will be GIVEN Statement Reason 1) Given 1) 2x + 5 = 17
Given: 2x+5=17Prove x=6 Statement Reason 1) Given 1) 2x + 5 = 17 2) Subtraction Property 2) 2x + 5 – 5 = 17 - 5
Given: 2x+5=17Prove x=6 Statement Reason 1) Given 1) 2x + 5 = 17 2) Subtraction Property 2) 2x + 5 – 5 = 17 - 5 3) Substitution 3) 2x = 12
Given: 2x+5=17Prove x=6 Statement Reason 1) Given 1) 2x + 5 = 17 2) Subtraction Property 2) 2x + 5 – 5 = 17 - 5 3) Substitution 3) 2x = 12 4) 2x / 2 = 12 / 2 4) Division Property
Given: 2x+5=17Prove x=6 Statement Reason 1) Given 1) 2x + 5 = 17 2) Subtraction Property 2) 2x + 5 – 5 = 17 - 5 3) Substitution 3) 2x = 12 4) 2x / 2 = 12 / 2 4) Division Property 5) X = 6 5) Substitution
Remember !! • The SHOW ME steps will be Add, Sub, Mult, or Div or Distributive Properties • The DO IT steps will be Substitution