X 2 4x 49 0 July 8, 2019 16 32 64 128 X 2 49 2 x 2 4x 21 0 Tìm x 4x 2 49 0 Tìm x biết 4x 2 49 0 2x 4x 7 )( x 2 49 )= 0
