设等差数列的前N项和为Sn,已知前6项和为36,Sn=324,最后6项的和为180(n>6)求数列的项数n及a9+a10
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![设等差数列的前N项和为Sn,已知前6项和为36,Sn=324,最后6项的和为180(n>6)求数列的项数n及a9+a10](/uploads/image/z/12629170-10-0.jpg?t=%E8%AE%BE%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%E7%9A%84%E5%89%8DN%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%E5%B7%B2%E7%9F%A5%E5%89%8D6%E9%A1%B9%E5%92%8C%E4%B8%BA36%2CSn%3D324%2C%E6%9C%80%E5%90%8E6%E9%A1%B9%E7%9A%84%E5%92%8C%E4%B8%BA180%EF%BC%88n%3E6%EF%BC%89%E6%B1%82%E6%95%B0%E5%88%97%E7%9A%84%E9%A1%B9%E6%95%B0n%E5%8F%8Aa9%2Ba10)
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