百度试题 结果1 题目若an=5,bn=8,则(ab)n= 40. 相关知识点: 试题来源: 解析 解:∵(ab)n=an•bn,又∵an=5,bn=8,∴(ab)n=5×8=40.故答案为:40. 运用幂的乘方、积的乘方运算法则求解即可.反馈 收藏
11.下图中AN 、BN属于两条相对的经线,N为北极,BC处于昼半球,C地纬度是66.5°,图中数据为纬度。 据图可知,此时(A)0° 20° 40° 60° 80° 8
分析:(Ⅰ)等差数列{an}中,由a5=-3,S10=-40,解得a1=5,d=-2.由此能求出数列{an}的通项公式. (Ⅱ)由{abn}为等比数列,b1=5,b2=8,知ab1=7-2b1=7-10=-3,ab2=7-2b2=7-16=-9,故abn=7-2bn=-3n,所以bn= 1 2 •3n+ 7 2 .cn= ...
已知等差数列{an}的前n项和为Sn,且a2=8,S4=40.数列{bn}的前n项和为Tn,且Tn-2bn+3=0,n∈N*.(Ⅰ)求数列{an},{bn}的通项公式;(Ⅱ)设cn=an,n为奇数bn,n为偶数,求数列{cn}的前2n+1项和P2n+1.
解：（Ⅰ）设等差数列{an}的公差为d，由题意，得a1+d=8 4a1+6d=40解得a1=4d=4∴an=4n，∵Tn-2bn+3=0，∴当n=1时，b1=3当n≥2时，Tn-1-2bn-1+3=0，两式相减，得bn=2bn-1，（n≥2）则数列{bn}为等比数列，∴bn=3•2n-1；（Ⅱ）cn=4n n为奇数3*2n-1 n...
试题解析:(Ⅰ)设等差数列{an}的公差为d,由题意,得 a1+d=8 4a1+6d=40 ,解得 a1=4 d=4 ,∴an=4n;∵Tn-2bn+3=0,∴当n≥2时,Tn-1-2bn-1+3=0,两式相减,得bn=2bn-1,(n≥2)又当n=1时,b1=3,则数列{bn}为等比数列,∴bn=3•2n-1; (Ⅱ) cn= 4n n为奇数 3•2n-1 n...
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解:(Ⅰ)设等差数列{an}的公差为d,由题意,得∠A,解得∠A,∴an=4n,∵Tn-2bn+3=0,∴当n=1时,b1=3,当n≥2时,Tn-1-2bn-1+3=0,两式相减,得bn=2bn-1,(n≥2)则数列{bn}为等比数列,∴∠ACB; (Ⅱ)∠ACB.当n为偶数时,Pn=(a1+a3+…+an-1)+(b2+b4+…+bn)=∠ACB=90°. 当n...
解：（Ⅰ）设等差数列{an}的公差为d，由题意，得 a1+d=8 4a1+6d=40 解得 a1=4d=4 ∴an=4n，∵Tn-2bn+3=0，∴当n=1时，b1=3 当n≥2时，Tn-1-2bn-1+3=0，两式相减，得bn=2bn-1，（n≥2）则数列{bn}为等比数列，∴bn=3•2n-1；（Ⅱ）cn=4n n为奇数 3*2...