等差数列{an}中,2(a2+a4+a6)+3(a8+a12)=36,那此数列前13项之和是?
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等差数列{an}中,2(a2+a4+a6)+3(a8+a12)=36,那此数列前13项之和是?
等差数列{an}中,2(a2+a4+a6)+3(a8+a12)=36,那此数列前13项之和是?
等差数列{an}中,2(a2+a4+a6)+3(a8+a12)=36,那此数列前13项之和是?
由等差数列性质可知,2(a2+a4+a6)+3(a8+a12)=2*3a4+3*2a10=6(a4+a10)=6(a1+a13)=36,所以a1+a13=6 而S13=(a1+a13)*13/2=39