# #Special Pythagorean triplet #Problem 9 # #A Pythagorean triplet is a set of three natural numbers, a < b < c, for which, # #a^2 + b^2 = c^2 #For example, 3^2 + 4^2 = 9 + 16 = 25 = 5^2. # #There exists exactly one Pythagorean triplet for which a + b + c = 1000. #Find the product abc. # #Solution: # # a^2+b^2=c^2=(1000-a-b)^2= 1000^2-2000(a+b)+(a+b)^2= # = 1000^2-2000(a+b)+a^2+2ab+b^2 => # => 0=1000^2-2000(a+b)+2ab => # => 500000=1000(a+b)-ab # => 500=a+b - ab/1000 # => ab is dividable to 1000=2*2*2*5*5*5 # => a dividable at least to 5 and b to 2 # #for a in range(5,1000,5): # for b in range(2,1000-a,2): # i+=1 # if (a**2+b**2) == (1000-a-b)**2: # print( a, b, 1000-a-b, '->', a**2, '+', b**2, '=', a**2+b**2 ) # print( ' while (1000-a-b)**2 =', (1000-a-b)**2 ) # print( 'product =', a*b*(1000-a-b) ) # print( 'product =', (a+b)*(5*10**5+10**3) - (a+b)**2 - 5*10**8 ) # # a better solution # => 500000=1000(a+b)-ab # => (500000-1000a)/(1000-a)=b # => 1000(500-a)/(1000-a)=b for a in range(1,500): r=1000*(500-a) q=1000-a b=r//q if (a**2+b**2) == (1000-a-b)**2: print( a, b, 1000-a-b, '->', a**2, '+', b**2, '=', a**2+b**2 ) print( ' while (1000-a-b)**2 =', (1000-a-b)**2 ) print( 'product =', a*b*(1000-a-b) ) print( 'product =', (a+b)*(5*(10**5)+10**3) - (a+b)**2 - 5*(10**8) )