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SimpleMulFacts
Nuprl Section: SimpleMulFacts - Some handy lemmas about integer multiplication.

Selected Objects
COMsimple_mul_factsVERSION
1
THMnat_prod_one_iff_factors_one
x,y:xy = 1  x = 1 & y = 1
THMprod_zero_iff_factor_zero
a,b:ab = 0  a = 0  b = 0
THMmul_nat_com
a,b,c,d:a = b  c = d  ac = db  
THMnat_factor_cancel_rw
a,b:n:nanb  ab
THMmul_cancel_in_eq1
a,b:n:na = nb  a = b
THMmul_cancel_in_eq2
a,b:m,n:m = n  (ma = nb  a = b)
THMle_mul_rt_by_pos
x,y:z:xy  xyz
THMfactor_bound
k:n:x,y:kx+n = ky  xy
THMlt_mul_rt_by_pos
x,y:z:x<y  x<yz
THMfactors_bound
i,j:iij & jij
THMpos_mul_arg_boundsNat
a,b:. 0<ab  0<a & 0<b
THMpos_mul_arg_boundsNat2
i,j:. 0<ij  iij & jij
THMfactor_smaller
i:{2...}, j:{1...}. j<ij
THMfactor_smaller2
i:{2...}, j:j<ij
THMfactors_smaller
i,j:{2...}. i<ij & j<ij
THMfactors_smaller2
k:i:{2..k}, j:ij = k  2  j < k & i<k
THMmul_nat_plus
x,y:xy  
THMdivides_def_on_nat
a divides b (specialized to natural numbers)
a,b:a | b  (c:b = ac)
THMonly_one_nat_divs_one
b:b | 1  b = 1
THMdiv_inverts_nat_mul
x,y:z:x = yz  (x  z) = y
THMdiv_inverts_nat_mul2
x:y,z:x = yz  (x  z) = y
THMprime_nat
x:. prime(x 2x & (i:{2..x}. i | x)
defprime_nats
Prime == {x:| prime(x) }
THMnatprimes_lb
x:. prime(x 2x
THMnatprime_nondivs
x:. prime(x (i:{2..x}. i | x)
THMnonprime_nat
x:prime(x x<2  (i,j:{2..x}. x = ij)
THMcomposite_with_prime_factor
x:{2...}. prime(x (i,j:{2..x}. x = ij & prime(i))
THMprime_or_smaller_prime_factor2
x:{2...}. p:{2...}, c:{1...}. px & prime(p) & x = pc
THMprime_or_smaller_prime_factor
A number bigger than 1 is divisible by a prime.
x:{2...}. p:{2...}. px & prime(p) & p | x
THMprime_neg
y:. prime(-y prime(y)
THMdecidable__prime
x:. Dec(prime(x))
THMprime_decider_exists
!{p:()| x:p(x prime(x) }
defprime_decider
Boolean decider for primeness implicit in Thm*  !{p:()| x:p(x prime(x) }
is_prime(x) == prime_decider_exists{1:l}(x)
THMno_nat_prime_divs_one
b:b | 1  prime(b)
THMno_prime_divs_one
One has no prime divisors.
b:b | 1  prime(b)
THMno_prime_divs_one_b
One has no prime divisors.
b:. prime(b b | 1
THMprime_nat_divby_self_only
x:{2...}, y:. prime(y x | y  x = y  
THMprime_among_factors
Factoring a prime always includes the prime itself.
a,b:. prime(ab ab = a  ab = b
IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html

Origin Definitions Sections DiscrMathExt Doc