tìm ba số x,y,z bt rằng : \(\dfrac{x}{5}=\dfrac{y}{3}=\dfrac{z}{2}\) và x+2y+3z=34
giúp mk vs 12h 45' đi thi oy
1) Rút gọn p/s:
a) 6*9 - 2*17 / 63*3 - 119
b) 2*3 + 4*6 + 14*21 / 3*5 + 6*10 + 21*35
c) 3*13 - 13*18 / 15*40 - 80
d) (-5)^3*40*4^3 / 135 * (-2)^14 * (-100)^0
e)18*34+(-18)*124 / -36 *17 +9*(-52)
d.\(\dfrac{123}{456}.\left(\dfrac{2010}{2011}-\dfrac{2011}{2010}\right)-\left(\dfrac{2009}{2010}-\dfrac{1}{2011}\right):\dfrac{456}{123}\)
b. Cho A = \(\dfrac{1}{2}+\dfrac{1}{12}+\dfrac{1}{30}+...+\dfrac{1}{2450}\)
Cho B = \(\dfrac{1}{26}+\dfrac{1}{27}+\dfrac{1}{28}+...+\dfrac{1}{50}\)
Tính A : B
f) \(-\dfrac{1}{30}-\dfrac{1}{15.13}-\dfrac{1}{13.11}-...-\dfrac{1}{5.3}-\dfrac{1}{3.1}\)
\(-\dfrac{1}{4}--5+\dfrac{1}{3}-\dfrac{3}{2}-3-\dfrac{7}{4}+\dfrac{4}{3}=?\)
\(\dfrac{1}{\sqrt{1}-\sqrt{2}}-\dfrac{1}{\sqrt{3}-\sqrt{4}}+\dfrac{1}{\sqrt{4}-\sqrt{5}}-\dfrac{1}{\sqrt{5}-\sqrt{6}}+\dfrac{1}{\sqrt{6}-\sqrt{7}}-\dfrac{1}{\sqrt{7}-\sqrt{8}}+\dfrac{1}{\sqrt{8}-\sqrt{9}}\)
a. Lập các tỉ lệ thức có thể có được từ đẳng thức sau : 18.96 = 64.27
b.Cho A = \(\dfrac{1}{2}+\dfrac{1}{12}+\dfrac{1}{30}+...+\dfrac{1}{2450}\)
Cho B = \(\dfrac{1}{26}+\dfrac{1}{27}+\dfrac{1}{28}+...+\dfrac{1}{50}\)
Tính A:B
c.\(\dfrac{5}{8}-\dfrac{3}{8}:\left(-\dfrac{3}{4}\right)-\dfrac{1}{4}\)
