············································· 1分 ?A(?2,0),B(2,0) ·又
点B在y??3x?b上 43?0???b
23b?
233······································································· 2分 ?BC的解析式为y??x? ·
4232?y??x?3?x1??1???4(2)由?,得?9
33y1??y??x???4??429???C??1,?,B(2,0)
4???x2?2 ·················································· 4分 ?y?0?29 ······················································································· 5分 4199················································································· 6分 ?S△ABC??4?? ·
242(3)过点N作NP?MB于点P EO?MB ?NP∥EO
······················································································ 7分 ?△BNP∽△BEO ·
BNNP ································································································· 8分 ??BEEO?AB?4,CD?由直线y??33?3?x?可得:E?0,? 42?2??在△BEO中,BO?2,EO?35,则BE? 2262tNP,?NP?t ················································································ 9分 ?5352216?S?t(4?t)
25312S??t2?t(0?t?4) ············································································· 10分
55312S??(t?2)2? ····················································································· 11分
5512此抛物线开口向下,?当t?2时,S最大?
5??当点M运动2秒时,△MNB的面积达到最大,最大为
12. ···························· 12分 5
巴中市中考题及答案



