RÚT GỌN
\(A=_{100}+5+5.9+5.9^2+5.9^3+...+5.9^{99}\)
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5 + 5.9+5.9^2+5.9^3+.....+5.9^99
Tính nhanh
a) A=4/1.5+4/5.9+...+4/2001.2005
b) B=3/10.12+3/1214+...+3/998.1000
Ai lm đc nhớ nghi lời, giải đầy đủ~
Cảm ơn!!!
\(A=\dfrac{4}{1\cdot5}+\dfrac{4}{5\cdot9}+...+\dfrac{4}{2001\cdot2005}\)
\(A=1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+\dfrac{1}{9}-...+\dfrac{1}{2001}-\dfrac{1}{2005}\)
\(A=1-\dfrac{1}{2005}=\dfrac{2004}{2005}\)
\(B=\dfrac{3}{10\cdot12}+\dfrac{3}{12\cdot14}+...+\dfrac{3}{998\cdot1000}\)
\(\dfrac{2}{3}B=\dfrac{2}{10\cdot12}+...+\dfrac{2}{998\cdot1000}\)
\(\dfrac{2}{3}B=\dfrac{1}{10}-\dfrac{1}{12}+\dfrac{1}{12}-...+\dfrac{1}{998}-\dfrac{1}{1000}\)
\(\dfrac{2}{3}B=\dfrac{1}{10}-\dfrac{1}{1000}=\dfrac{99}{1000}\)
\(B=\dfrac{99}{1000}:\dfrac{2}{3}=\dfrac{297}{2000}\)
\(A=\dfrac{4}{1.5}+\dfrac{4}{5.9}+...+\dfrac{4}{2001.2005}\)
\(\Rightarrow A=4\left(\dfrac{1}{1.5}+\dfrac{1}{5.9}+...+\dfrac{1}{2001.2005}\right)\)
\(\Rightarrow A=4.\dfrac{1}{4}\left(1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+...+\dfrac{1}{2001}-\dfrac{1}{2005}\right)\)
\(\Rightarrow A=1-\dfrac{1}{2005}\)
\(\Rightarrow A=\dfrac{2004}{2005}\)
\(B=\dfrac{3}{10.12}+\dfrac{3}{12.14}+...+\dfrac{3}{998.1000}\)
\(\Rightarrow B=3\left(\dfrac{1}{10.12}+\dfrac{1}{12.14}+...+\dfrac{1}{998.1000}\right)\)
\(\Rightarrow B=3.\dfrac{1}{2}\left(\dfrac{1}{10}-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{12}+...+\dfrac{1}{998}-\dfrac{1}{1000}\right)\)
\(\Rightarrow B=\dfrac{3}{2}\left(\dfrac{1}{10}-\dfrac{1}{1000}\right)\)
\(\Rightarrow B=\dfrac{3}{2}.\dfrac{99}{1000}\)
\(\Rightarrow B=\dfrac{297}{2000}\)
Rút gọn A=\(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
các bạn ghi cách giải cho mk nha
Rút gọn biểu thức \(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
Giúp mình nha mình tích đúng cho
AI KẾT BN KO!
TIỆN THỂ TK MÌNH LUÔN NHA!
KONOSUBA!!!
AI TK MÌNH MÌNH TK LẠI 3 LẦN.
\(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
\(=\frac{\left(2^2\right)^5.\left(3^2\right)^4-2.6^9}{2^{10}.3^8+\left(2.3\right)^8.2^2.5}\)
\(=\frac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+2^{10}.3^8.5}\)
\(=\frac{2^{10}.3^8\left(1-3\right)}{2^{10}.3^8\left(1+5\right)}\)
\(=\frac{-2}{6}\)
\(=-\frac{1}{3}\)
Rút gọn : A = 4^5.9^4-2.6^9\2^10.3^8+6^8.20
rút gọn:
\(A=\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
\(A=\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
\(A=\frac{\left(2^2\right)^5.\left(3^2\right)^4-2.\left(2.3\right)^9}{2^{10}.3^8+\left(2.3\right)^8.2^2.5}\)
\(A=\frac{2^{10}.3^8-2.2^9.3^9}{2^{10}.3^8+2^8.3^8.2^2.5}\)
\(A=\frac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+2^{10}.3^8.5}\)
\(A=\frac{2^{10}.3^8.\left(1-3\right)}{2^{10}.3^8.\left(1+5\right)}\)
\(A=\frac{2^{10}.3^8.\left(-2\right)}{2^{10}.3^8.6}\)
\(A=-\frac{2^{11}.3^8}{2^{10}.3^8.2.3}=-\frac{2^{11}.3^8}{2^{11}.3^9}=-\frac{1}{3}\)
rút gọn P=14^5.9^4-6^9.49^2/2^10.49^3.3^8+6^8.7^5.13
Giúp với giải thích đầy đủ nha !! Mik sẽ tick ..
bài 1 :
H = 3/1.5 + 3/5.9 + 3/9.13 + ... + 3/33.37
Tính H hộ nha !!
Bài 2 :
1/3.5 + 1/5.7 + 1/7.9 + ... + 1/ (2x + 1 ) . ( 2x + 3 ) = 15/93
Giải đầy đủ hộ nha !
2.
\(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{\left(2x+1\right).\left(2x+3\right)}=\frac{15}{93}\)
\(\Rightarrow\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{5}\right)+\frac{1}{2}.\left(\frac{1}{5}-\frac{1}{7}\right)+\frac{1}{2}.\left(\frac{1}{7}-\frac{1}{9}\right)+...+\frac{1}{2}.\left(\frac{1}{2x+1}-\frac{1}{2x+3}\right)=\frac{15}{93}\)
\(\Rightarrow\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{2x+1}-\frac{1}{2x+3}\right)=\frac{15}{93}\)
\(\Rightarrow\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{2x+3}\right)=\frac{15}{93}\)
\(\Rightarrow\frac{1}{3}-\frac{1}{2x+3}=\frac{15}{93}:\frac{1}{2}\)
\(\Rightarrow\frac{1}{3}-\frac{1}{2x+3}=\frac{10}{31}\)
\(\Rightarrow\frac{1}{2x+3}=\frac{1}{3}-\frac{10}{31}\)
\(\Rightarrow\frac{1}{2x+3}=\frac{1}{93}\)
\(\Rightarrow\)2x + 3 = 93
\(\Rightarrow\)2x = 93 - 3
\(\Rightarrow\)2x = 90
\(\Rightarrow\)x = 90 : 2 = 45
\(H=\frac{3}{1.5}+\frac{3}{5.9}+\frac{3}{9.13}+...+\frac{3}{33.37}\)
= \(\frac{3}{4}\left(1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{33}-\frac{1}{37}\right)\)
= \(\frac{3}{4}\left(1-\frac{1}{37}\right)\)
= \(\frac{3}{4}.\frac{36}{37}=\frac{27}{37}\)
Tính:
a) \(\dfrac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
b) T=\(\dfrac{5^{16}.27^7}{125^5.9^{11}}\)
a: \(=\dfrac{2^{10}\cdot3^8-2^{10}\cdot3^9}{2^{10}\cdot3^8+2^{10}\cdot3^8\cdot5}=\dfrac{2^{10}\cdot3^8\left(1-3\right)}{2^{10}\cdot3^8\left(1+5\right)}=\dfrac{-2}{6}=\dfrac{-1}{3}\)
b: \(=\dfrac{5^{16}\cdot3^{21}}{5^{15}\cdot3^{22}}=\dfrac{5}{3}\)