Question

求：2009嘉兴中考数学最后一题答案

Answer 1

24.（1）在三角形ABC中 因为AC=，AB=x，BC=3-x.
所以1+x大于3-x 1+3-x大于x 解得1小于x小于2
（2）x=5/3或x=4/3
(3)面积最大为二分之根号二
很抱歉 有些符号打不出 答案估计返校日老师会给的

Answer 2

第一题，大于1小于2，第2题，三分之5，三分之4，第3题2分之根号2。这是标准答案！

Answer 3

（1）在△ABC中，∵1=AC，xAB=，xBC−=3．
∴>−+−>+xxxx3131，解得21<<x． ······················································································ 4分 （2）①若AC为斜边，则22)3(1xx−+=，即0432=+−xx，无解． ②若AB为斜边，则1)3(22+−=xx，解得35=x，满足21<<x． ③若BC为斜边，则221)3(xx+=−，解得34=x，满足21<<x． ∴35=x或34=x． ·············································································································· 9分 3）在△ABC中，作ABCD⊥于D， 设hCD=，△ABC的面积为S，则xhS21=． ①若点D在线段AB上， 则xhxh=−−+−222)3(1． ∴22222112)3(hhxxhx−+−−=−−，即4312−=−xhx． ∴16249)1(222+−=−xxhx，即16248222−+−=xxhx． ∴462412222−+−==xxhxS21)23(22+−−=x（423x<≤）． ································ 11分 当23=x时（满足423x<≤），2S取最大值21，从而S取最大值22． ························ 13分 ②若点D在线段MA上， 则xhhx=−−−−2221)3(． 同理可得，462412222−+−==xxhxS 21)23(22+−−=x（413x<≤）， 易知此时22<S． 综合①②得，△ABC的最大面积为22． ·········································································· 14分
有些符号打不出

Answer 4

海伦公式最简单!