设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13= 简便方法怎么算出a1+a2+a3+(11-1)3d在得出d=3后怎么得到a1+a2+a3+(11-1)3d这一步
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![设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13= 简便方法怎么算出a1+a2+a3+(11-1)3d在得出d=3后怎么得到a1+a2+a3+(11-1)3d这一步](/uploads/image/z/1775501-53-1.jpg?t=%E8%AE%BE%7Ban%7D%E6%98%AF%E5%85%AC%E5%B7%AE%E4%B8%BA%E6%AD%A3%E6%95%B0%E7%9A%84%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E8%8B%A5a1%2Ba2%2Ba3%3D15%2Ca1a2a3%3D80%E5%88%99a11%2Ba12%2Ba13%3D+%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%E6%80%8E%E4%B9%88%E7%AE%97%E5%87%BAa1%2Ba2%2Ba3%2B%2811-1%293d%E5%9C%A8%E5%BE%97%E5%87%BAd%3D3%E5%90%8E%E6%80%8E%E4%B9%88%E5%BE%97%E5%88%B0a1%2Ba2%2Ba3%2B%2811-1%293d%E8%BF%99%E4%B8%80%E6%AD%A5)
设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13= 简便方法怎么算出a1+a2+a3+(11-1)3d在得出d=3后怎么得到a1+a2+a3+(11-1)3d这一步
设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13= 简便方法
怎么算出a1+a2+a3+(11-1)3d
在得出d=3后怎么得到a1+a2+a3+(11-1)3d这一步
设{an}是公差为正数的等差数列,若a1+a2+a3=15,a1a2a3=80则a11+a12+a13= 简便方法怎么算出a1+a2+a3+(11-1)3d在得出d=3后怎么得到a1+a2+a3+(11-1)3d这一步
a1+a2+a3=3a2=15
a2=5
a1+a3=10 a1*a3=16
由此可得a1=2,a3=8(因为公差为正数,故a1
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