1.已知等差数列{an}的公差为1,且a1+a2+a3+……+a99=99,则a3+a6+…+a99的值为( )A.99 B.66 C.33 D.02.已知等差数列{an}的公差d=1/2,a1+a3+a5+a7+a9+…+a95+a97+a99=60,则前100项之和S100等于( )A.120 B.145.C.150 D.1703.等
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![1.已知等差数列{an}的公差为1,且a1+a2+a3+……+a99=99,则a3+a6+…+a99的值为( )A.99 B.66 C.33 D.02.已知等差数列{an}的公差d=1/2,a1+a3+a5+a7+a9+…+a95+a97+a99=60,则前100项之和S100等于( )A.120 B.145.C.150 D.1703.等](/uploads/image/z/1770980-68-0.jpg?t=1.%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%85%AC%E5%B7%AE%E4%B8%BA1%2C%E4%B8%94a1%2Ba2%2Ba3%2B%E2%80%A6%E2%80%A6%2Ba99%3D99%2C%E5%88%99a3%2Ba6%2B%E2%80%A6%2Ba99%E7%9A%84%E5%80%BC%E4%B8%BA%EF%BC%88+%EF%BC%89A.99+B.66+C.33+D.02.%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%85%AC%E5%B7%AEd%3D1%2F2%2Ca1%2Ba3%2Ba5%2Ba7%2Ba9%2B%E2%80%A6%2Ba95%2Ba97%2Ba99%3D60%2C%E5%88%99%E5%89%8D100%E9%A1%B9%E4%B9%8B%E5%92%8CS100%E7%AD%89%E4%BA%8E%EF%BC%88+%EF%BC%89A.120+B.145.C.150+D.1703.%E7%AD%89)
1.已知等差数列{an}的公差为1,且a1+a2+a3+……+a99=99,则a3+a6+…+a99的值为( )A.99 B.66 C.33 D.02.已知等差数列{an}的公差d=1/2,a1+a3+a5+a7+a9+…+a95+a97+a99=60,则前100项之和S100等于( )A.120 B.145.C.150 D.1703.等
1.已知等差数列{an}的公差为1,且a1+a2+a3+……+a99=99,则a3+a6+…+a99的值为( )
A.99 B.66 C.33 D.0
2.已知等差数列{an}的公差d=1/2,a1+a3+a5+a7+a9+…+a95+a97+a99=60,则前100项之和S100等于( )
A.120 B.145.C.150 D.170
3.等差数列{an}中,前4项和为26,后4项之和为110,且n项和为187,则n的值为( )
1.已知等差数列{an}的公差为1,且a1+a2+a3+……+a99=99,则a3+a6+…+a99的值为( )A.99 B.66 C.33 D.02.已知等差数列{an}的公差d=1/2,a1+a3+a5+a7+a9+…+a95+a97+a99=60,则前100项之和S100等于( )A.120 B.145.C.150 D.1703.等
a1+a2+a3+.+a99=99
--->99a1+99*98d/2=99
--->a1+49d=1
a3+a6+a9+.+a99
=33a3+33*32*3d/2
=33(a3+48d)
=33(a1+50d)=33(1+d)=33*2=66
a2=a1+d
a4=a3+d
.
a100=a99+d
a2+a4+...a100=a1+a3+...+a99+50d=60+25=85
S100=60+85=145
a1+an=a5+an-4 (n-4)为下标
187/n=(187-26-110)/(n-8)
n=11