Hệ phương trình bậc nhất

Qui tă ́ c thê ́ : Qui tă ́ c thê ́ :                                              !  "      #          !  "      #   $       %   $       %                                                                 &   & '        (   '        (                                              (    !         !   "            (    !         !   "       #  $      !       #  $      !   )  "  *      +   & & , - &  , -            − = = + =    ⇔ ⇔    + = + + = =    )  (+.            + /0( 1&0     *        2+ 3 & , & , & & 4            + = − =     + = − =   , 5 - , 3 & & - 4 &           − = − =     + = + =   , &  & ,  4 3 , , &            − = − =     − = + =    Qui tă ́ c cô ̣ ng: Qui tă ́ c cô ̣ ng:    +    +  6   (       %        6   (       %                                                     &+   &+ '        (   '        (                                           %    (  $ %    (  $ )  "  *      + )  "  *      + , 4 7 & , 3 ,            + = = =    ⇔ ⇔    − = + = =    & , 8 & , 8 5 3 , , 3             + = + = =    ⇔ ⇔    + = + = = −    , 4 9 8 & ,9 4 ,  5 & 44 - 4 & , 4 9                + = + =   ⇔   + = + =   = =   ⇔ ⇔   + = =   Ba ̀ i tâ ̣ p*      + , , & 3 7 & - & , 9           + = − =     − = − =   & , & 9:, 9:3 , , & , :3 & :3           + = − + =     − = − − =   & ,  3 , & & & & & 5 & &             − = + =     + = − − =     )  "  *       ,  & , , & 5  , 4 5 , 9                   + + = =   + =    + + = ⇔ ⇔ =    + =    + + = =   , & 9  5 & 9 5 8 ,- & - 3 - 8 4 &9 ,                  + + = =   + =    + + = ⇔ ⇔ =    + =    + + = =  