Question

x+3x+5x+...+1997x=2x+4x+6x+....+1996x+9990=​

Answer 1

x+3x+5x+...+1997x = 2x+4x+6x+....+1996x+9990

x·(1+3+5+...+1997) = x·(2+4+6+...+1996) + 9990

x·(1+3+5+...+1997) - x·(2+4+6+...+1996) = 9990

x·(1-0+3-2+5-4+7-6+...+1997-1996) = 9990

x·(1+1+1+...+1) = 9990  {1 de (1997+1)/2 = 999 ori}

x·999 = 9990

x = 9990:999

x = 10