导学案,帮忙解答下高一数学题,,谢了,,答案写清楚哦!!急急急!!!!两题!!
\u5bfc\u5b66\u6848\uff0c\u5e2e\u5fd9\u89e3\u7b54\u4e0b\u9ad8\u4e00\u6570\u5b66\u9898\uff0c\uff0c\u8c22\u4e86\uff0c\uff0c\u7b54\u6848\u5199\u6e05\u695a\u54e6\uff01\uff01\u6025\u6025\u6025\uff01\uff01\uff01\uff01\u4e24\u9898\uff0c\uff0c\u56fe\u7247\u6ca1\u4f20\u4e0a\u6765\u3002
\u2235a\u3001b\u5747\u4e3a\u5355\u4f4d\u5411\u91cf\u4e14\u5b83\u4eec\u7684\u5939\u89d2\u4e3a60\u00b0\u2234|a-3b|\uff1d\u221a[a-3b]²\uff1d\u221a[a²-6a•b\uff0b9b²]\uff1d\u221a[1\uff0b9-6|a||b|cos60\u00b0]\uff1d\u221a[1\uff0b9-6\u00d7(1/2)]\uff1d\u221a7
第一题无解,因为没有说明这是什么数列,这两个条件不足以求出答案。
第二题因为已经知道是等差数列,abc,其中a+c=2b,a+b+c=9,得出b=3,那么a+c=6,a=6-c,a^2+b^2+c^2=(6-c)^2+9+c^2=35,从而得出c^2-6c+5=0,解得c=1或5,验证一下就知道,c=1符合条件,所以a=5,c=5,则a=1,所以三个数就是5.,3,1。
采纳一部分吧。
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