Question

已知點(diǎn)A（a，2）與點(diǎn)B （-1，b）關(guān)于原點(diǎn)O對(duì)稱，則的值為    ．

Answer 1

【答案】分析：根據(jù)關(guān)于原點(diǎn)對(duì)稱的點(diǎn)的特點(diǎn)，可得a、b的值，進(jìn)而可得答案．
解答：解：根據(jù)題意，已知點(diǎn)A（a，2）與點(diǎn)B （-1，b）關(guān)于原點(diǎn)O對(duì)稱，
則a=-（-1）=1，b=-2，
故則的值為-．
點(diǎn)評(píng)：本題考查關(guān)于原點(diǎn)對(duì)稱的點(diǎn)的坐標(biāo)特點(diǎn)，注意與關(guān)于x、y軸對(duì)稱點(diǎn)的性質(zhì)的區(qū)分記憶．