5^2x-3-8.5^3=17.5^3
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a) \(\dfrac{8,5-8,2}{16}=\dfrac{0,3}{16}=\dfrac{0,3\cdot10}{16\cdot10}=\dfrac{3}{160}\)
b) \(\dfrac{17\cdot5-17}{3-20}=\dfrac{17\cdot\left(5-1\right)}{-17}=\dfrac{1\cdot4}{-1}=-4\)
a)
\(\dfrac{8\cdot5-8\cdot2}{16}=\dfrac{8\left(5-2\right)}{16}=\dfrac{3}{2}\)
b)
\(\dfrac{17\cdot5-17}{3-20}=\dfrac{17\left(5-1\right)}{-17}=\dfrac{4}{-1}=-4\)
a. \(\dfrac{8,5-8,2}{16}=\dfrac{0,3}{16}=\dfrac{3}{160}\)
b. \(\dfrac{2\cdot14}{7\cdot8}=\dfrac{1\cdot2}{1\cdot4}=\dfrac{2}{4}=\dfrac{1}{2}\)
c. \(\dfrac{11\cdot4-11}{2-13}=\dfrac{11\left(4-1\right)}{-11}=\dfrac{1\cdot3}{-1}=-3\)
d. \(\dfrac{49+7\cdot49}{49}=\dfrac{49\cdot\left(1+7\right)}{49}=\dfrac{8}{1}=8\)
720 : [41 - (2x - 5)] = 8 . 5
=> 720 : [41 - (2x - 5)] = 40
=> 41 - (2x - 5) = 720 : 40
=> 41 - (2x - 5) = 18
=> 2x - 5 = 41 - 18
=> 2x - 5 = 23
=> 2x = 23 + 5
=> 2x = 28
=> x = 28 : 2
=> x = 14
Vậy x = 14
1 + 2 + 3 + 4 + ... + (x - 1) + x = 78
có x số hạng
=> (x + 1) . x : 2 = 78
=> (x + 1) . x = 78 . 2
=> (x + 1) . x = 156
=> (x + 1) . x = 13 . 12
=> x = 12
Vậy x = 12
a)720:[41-(2x-5)]=40
41-(2x-5)=720:40
41-(2x-5)=18
2x-5=41-18
2x-5=23
2x=28
x=14
\(A=3125+625-8.125\)
\(A=\left(3125+625\right)-1000\)
\(A=3750-1000\)
\(A=2750\)
b) Ta có: \(B=\dfrac{7}{8}\cdot\dfrac{4}{9}+\dfrac{7}{8}\cdot\dfrac{5}{9}\)
\(=\dfrac{7}{8}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)
\(=\dfrac{7}{8}\cdot1=\dfrac{7}{8}\)