src/HOL/ex/Commutative_RingEx.thy
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     1  (* $Id$ *)
       
     2 theory Commutative_RingEx
       
     3 imports Main
       
     4 begin
       
     5 
       
     6   (* Some examples demonstrating the comm_ring method *)
       
     7 
       
     8 lemma "4*(x::int)^5*y^3*x^2*3 + x*z + 3^5 = 12*x^7*y^3 + z*x + 243"
       
     9 by comm_ring
       
    10 
       
    11 lemma "((x::int) + y)^2  = x^2 + y^2 + 2*x*y"
       
    12 by comm_ring
       
    13 
       
    14 lemma "((x::int) + y)^3  = x^3 + y^3 + 3*x^2*y + 3*y^2*x"
       
    15 by comm_ring
       
    16 
       
    17 lemma "((x::int) - y)^3  = x^3 + 3*x*y^2 + (-3)*y*x^2 - y^3"
       
    18 by comm_ring
       
    19 
       
    20 lemma "((x::int) - y)^2  = x^2 + y^2 - 2*x*y"
       
    21 by comm_ring
       
    22 
       
    23 lemma " ((a::int) + b + c)^2 = a^2 + b^2 + c^2 + 2*a*b + 2*b*c + 2*a*c"
       
    24 by comm_ring
       
    25 
       
    26 lemma "((a::int) - b - c)^2 = a^2 + b^2 + c^2 - 2*a*b + 2*b*c - 2*a*c"
       
    27 by comm_ring
       
    28 
       
    29 lemma "(a::int)*b + a*c = a*(b+c)"
       
    30 by comm_ring
       
    31 
       
    32 lemma "(a::int)^2 - b^2 = (a - b) * (a + b)"
       
    33 by comm_ring
       
    34 
       
    35 lemma "(a::int)^3 - b^3 = (a - b) * (a^2 + a*b + b^2)"
       
    36 by comm_ring
       
    37 
       
    38 lemma "(a::int)^3 + b^3 = (a + b) * (a^2 - a*b + b^2)"
       
    39 by comm_ring
       
    40 
       
    41 lemma "(a::int)^4 - b^4 = (a - b) * (a + b)*(a^2 + b^2)"
       
    42 by comm_ring
       
    43 
       
    44 lemma "(a::int)^10 - b^10 = (a - b) * (a^9 + a^8*b + a^7*b^2 + a^6*b^3 + a^5*b^4 + a^4*b^5 + a^3*b^6 + a^2*b^7 + a*b^8 + b^9 )"
       
    45 by comm_ring
       
    46 
       
    47 end