詢問幾道數(shù)學(xué)題啊
1.在等比數(shù)列｛an}中,已知a3+a8=124,a4a7=-512且公比為整數(shù),求a10
2.在等比數(shù)列｛an}中,已知a4=2,求前7項(xiàng)的積
3.若等比數(shù)列的首相為9/8,末項(xiàng)為1/3,公比為2/3,求該數(shù)列的項(xiàng)數(shù)
4.已知abc 成等差數(shù)列,a+b+c=12,且a,b,c+2成等比數(shù)列,求a
5.已知數(shù)列｛an｝滿足a1=1,a2=2,an+2=an+(an+1）/2令bn=an+1-an(1).求證｛bn}是等比數(shù)列（2）求｛an｝通項(xiàng)公式
6.已知數(shù)列｛an｝的前n相和Sn=10-n²,2bn=絕對值an,求｛bn｝的前n項(xiàng)和Tn
7.已知數(shù)列｛an｝的前n項(xiàng)和Sn=n²-9n,若5