1 ĐI MỂ ( 1+3+5+7+…+2003+2005) X (125 125 X 127 – 127 127 X 125) ...
Câu 4: 1 đi mể ( 1+3+5+7+…+2003+2005) x (125 125 x 127 – 127 127 x 125) = ( 1+3+5+7+…+2003+2005) x (125 x 1001 x 127 – 127 x 1001x 125) = ( 1+3+5+7+…+2003+2005) x 0 = 0