B=5(1/12−1/21+1/21−1/30)−5(1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64)
B=5(1/12−1/21+1/21−1/30+1/24−1/34+1/34−1/44+1/44−1/54+1/54−1/64 )
B=5(1/12−1/64)=5.13/192=65/192
cho các biểu thức
A=\(\left(\frac{1}{8\cdot14}+\frac{1}{14\cdot20}+\frac{1}{20\cdot26}+...+\frac{1}{50\cdot56}\right)\)
\(B=\left(\frac{45}{12\cdot21}+\frac{45}{21\cdot30}+\frac{40}{24\cdot34}-\frac{40}{34\cdot44}-\frac{40}{44\cdot54}-\frac{40}{54\cdot64}\right)\)
Chứng minh rằng:\(\frac{A}{B}< \frac{1}{8}\)
\(\frac{15}{X-9}=\frac{20}{Y-12}=\frac{40}{X-24},x.y=1200\)
Chứng minh rằng \(\frac{A}{B}\) < \(\frac{1}{8}\) A= \(\frac{1}{8.14}\) + \(\frac{1}{14.20}\) + \(\frac{1}{20.26}\) +...+ \(\frac{1}{50.56}\)
B= \(\frac{45}{12.21}\) + \(\frac{45}{21.30}\) -\(\frac{40}{24.34}\) -\(\frac{40}{34.44}\) \(\frac{40}{44.54}\) \(\frac{40}{54.64}\)
1.Tính:
a/ \(\frac{20^{12}\cdot6^{14}}{8^{13}\cdot15^{12}}\)
b/\(\frac{45^{12}\cdot10^{14}}{18^{13}\cdot25^{12}}\)
c/\(\frac{18^{12}\cdot27^8}{6^8\cdot3^{40}}\)
d/\(\frac{12^{14}\cdot9^{18}}{8^9\cdot27^{17}}\)
\(\frac{15}{x-9}=\frac{20}{y-12}=\frac{40}{z-24}\) và x.y =1200
Tìm x,y,z biết: \(\frac{15}{x-9}=\frac{20}{y-12}=\frac{40}{z-24};xy=1200\)
\(\frac{15}{x-9}=\frac{20}{y-12}=\frac{40}{z-24}vàx.y=1200\)giúp mình bài này với nha m.n
Tìm x,y ,z biết :\(\frac{15}{x-9}=\frac{20}{y-12}=\frac{40}{z-24}\) và xy=1200
Tìm x , y sao cho \(\frac{15}{x-9}=\frac{20}{y-12}=\frac{40}{z-24}\) và xy = 1200
