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5.( )在數線上O為原點,A點的坐標為a,B點的坐標為b,已知A、B、O三點在數線上的位置關係如右圖,則下列敘述何者正確?(A) │a│<│b│ (B) a × b <0 (C) a-b<0 (D) a+b>0
https://lh7-rt.googleusercontent.com/docsz/AD_4nXcTzMEJEDKwNd047S-nFqsFWYJJllRqLTRnAmRoXvsS4Po2El9yhK9DAjyB7k4i-PzpltD8l-VWsFQxKO_w7snTSI9pJA0lNvnG15iqL2rQqzO4PN0lzFipLrjaubXEENW1j8mGc8aNp2tBQJ4MknH4kKF9s1bS13EIYn_G0ej1lBJSNhKIYg?key=QJ9WUHc9fQMr7KOPMVGP4w
$\left\{\begin{array}{l}5 x-7 y=21 \\ 4 x-2 y=17 \end{array}\right.$ vs \left\{\begin{array}{l}5 x-7 y=21 \\ 4 x-2 y=17 \end{array}\right
(1) 2x-3y=6 , x-y=5
(2) +3
(3) (2,3)