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Chứng minh rằng
\(\frac{1\cdot3\cdot5\cdot\cdot\cdot\left(2n-1\right)}{\left(n+1\right)\cdot\left(n+2\right)\cdot\left(n+3\right)\cdot...\cdot2n}=\frac{1}{2^n}\)
Chứng minh rằng :
\(\frac{1\cdot3\cdot5\cdot...\cdot\left(2n-1\right)}{\left(n+1\right)\cdot\left(n+2\right)\cdot\left(n+3\right)\cdot...\cdot2n}=\frac{1}{2^n}\)
Chứng minh rằng:
a)\(\frac{1\cdot3\cdot5\cdot\cdot\cdot39}{21\cdot22\cdot23\cdot\cdot\cdot40}=\frac{1}{2^{20}}\)
b)\(\frac{1\cdot3\cdot5\cdot\cdot\cdot\left(2n-1\right)}{\left(n+1\right)\left(n+2\right)\left(n+3\right)\cdot\cdot\cdot2n}=\frac{1}{2^n}\)Với \(n\inℕ^∗\)
\(\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+\frac{1}{5\cdot7}+...+\frac{1}{\left(2n+1\right)\cdot\left(2n+3\right)}=\frac{n+1}{n+3}\)
Với n là số tự nhiên khác 0; Chứng minh \(\dfrac{1\cdot3\cdot5...\left(2n-1\right)}{\left(n+1\right)\left(n+2\right)\left(n+3\right)...\left(n+n\right)}=\dfrac{1}{2^n}\)
Help me please!
Bài 1 : Tìm nin Na) frac{4n-1}{3n+2}in N b) frac{5n-7}{2n+1}in NBài 2 : Tìm nin Na) left(n+2right)cdotleft(2n+5right)21 b) left(2n-3right)cdotleft(n-5right)22Bài 3 : Tìm x.yin Na) left(2n+1right)cdotleft(3y-5right)12 b) left(3x-1right)cdotleft(4y+3right)14Cách bạn giải ra giúp mình nha !
Đọc tiếp
Bài 1 : Tìm \(n\in N\)
a) \(\frac{4n-1}{3n+2}\in N\) b) \(\frac{5n-7}{2n+1}\in N\)
Bài 2 : Tìm \(n\in N\)
a) \(\left(n+2\right)\cdot\left(2n+5\right)=21\) b) \(\left(2n-3\right)\cdot\left(n-5\right)=22\)
Bài 3 : Tìm \(x.y\in N\)
a) \(\left(2n+1\right)\cdot\left(3y-5\right)=12\) b) \(\left(3x-1\right)\cdot\left(4y+3\right)=14\)
Cách bạn giải ra giúp mình nha !
Chứng minh rằng:
\(\frac{1.3.5.7.9.....\left(2n-1\right)}{\left(n+1\right)\left(n+2\right)\left(n+3\right).....2n}=\frac{1}{2^n}\)
Tính tổng :a) Afrac{5}{2cdot1}+frac{4}{1cdot11}+frac{3}{11cdot14}+frac{1}{14cdot15}+frac{13}{15cdot28}b) Bfrac{-1}{20}+frac{-1}{30}+frac{-1}{42}+frac{-1}{56}+frac{-1}{72}+frac{-1}{90}c) Cfrac{1}{1cdot2cdot3}+frac{1}{2cdot3cdot4}+...+frac{1}{nleft(n+1right)left(n+2right)}d) Dfrac{1}{1cdot2cdot3cdot4}+frac{1}{2cdot3cdot4cdot5}+...+frac{1}{nleft(n+1right)left(n+2right)left(n+3right)}e) Eleft(frac{1}{1cdot2cdot3}+frac{1}{2cdot3cdot4}+...+frac{1}{37cdot38cdot39}right)cdot1482cdot185cdot8
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Tính tổng :
a) \(A=\frac{5}{2\cdot1}+\frac{4}{1\cdot11}+\frac{3}{11\cdot14}+\frac{1}{14\cdot15}+\frac{13}{15\cdot28}\)
b) \(B=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
c) \(C=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+...+\frac{1}{n\left(n+1\right)\left(n+2\right)}\)
d) \(D=\frac{1}{1\cdot2\cdot3\cdot4}+\frac{1}{2\cdot3\cdot4\cdot5}+...+\frac{1}{n\left(n+1\right)\left(n+2\right)\left(n+3\right)}\)
e) \(E=\left(\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+...+\frac{1}{37\cdot38\cdot39}\right)\cdot1482\cdot185\cdot8\)
CMR \(\frac{1.3.5.7............\left(2n-1\right)}{\left(n+1\right).\left(n+2\right).\left(n+3\right)............2n}\)=\(\frac{1}{2^n}\)