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Lê Quốc Trần Anh Coordinator
13/06/2018 at 02:06
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Prove that: \(2\left(a^8+b^8\right)\ge\left(a^3+b^3\right)\left(a^5+b^5\right)\)


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Mr Puppy
14/07/2018 at 06:21
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Five pirates have obtained 100 gold coins and have to divide up the loot. The pirates are all extremely intelligent, treatrous and selfish (especially the captain). The captain always proposes a distribution of the loot. All pirates vote on the proposal and if at least half of the crew (which includes himself) approve, the loot will be divided as proposal, as no pirates would be willing to take on the captain without superior force on their side. Otherwise he will face a mutiny: all pirates will turn against him and make him walk the plank. The pirates will start over again with the next senior pirate as captain. What's the maximum number of coins the captain can keep without risking his life?

Maximum


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Bookname
04/08/2018 at 01:30
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1
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In the song "Golden Love", the author of "Do not separate each other" do what?

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    Cristiano Ronaldo 04/08/2018 at 01:31

    In the song "Golden Love", the author of "Do not separate each other" do what?

    Answer: Make ashes

    Bookname selected this answer.

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Love Anime
22/03/2017 at 17:54
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7
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A = 1 +\(\dfrac{1}{2}\)(1 + 2) +\(\dfrac{1}{3}\)(1 + 2 + 3) + ... +\(\dfrac{1}{2017}\)(1 + 2 + 3 + ... + 2017)

B = (2\(\dfrac{5}{6}\)+\(\dfrac{4}{9}\)): (10\(\dfrac{1}{12}\)-9\(\dfrac{1}{2}\))

C = 1\(\dfrac{5}{18}\):\(\dfrac{5}{18}\)(\(\dfrac{1}{15}\)+1\(\dfrac{1}{12}\))

D = -\(\dfrac{1}{7}\)(9\(\dfrac{1}{2}\)-8,75):\(\dfrac{2}{7}\)+0.625: 1\(\dfrac{2}{3}\)

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    Nễu Lả Ánh 24/03/2017 at 17:36


     

    We have B=256+4910112−912B=256+4910112−912

    =176+4912112−192=176+4912112−192

    =5118+81812112−11412=5118+81812112−11412

    =598712=598712

    =59.127.8=17714=59.127.8=17714

    Ans : B=17714B=17714.

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    ♫ ♪ ♥► EDM Troop ◄♥ ♪ ♫ 23/03/2017 at 11:34

    \(D=-\dfrac{1}{7}\left(9\dfrac{1}{2}-9,75\right):\dfrac{2}{7}+0,625:1\dfrac{2}{3}\)

    \(=\left(-1\right).\dfrac{1}{7}:\dfrac{2}{7}.\left(9,5-9,75\right)+\dfrac{5}{8}:\dfrac{5}{3}\)

    \(=-\dfrac{1}{2}.\left(-0,25\right)+\dfrac{3}{8}\)

    \(=\dfrac{1}{2}+\dfrac{3}{8}=\dfrac{4+3}{8}=\dfrac{7}{8}\)

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    ♫ ♪ ♥► EDM Troop ◄♥ ♪ ♫ 23/03/2017 at 11:31

    \(C=1\dfrac{5}{18}:\dfrac{5}{18}\left(\dfrac{1}{15}+1\dfrac{1}{12}\right)\)

    \(=\dfrac{23}{18}:\dfrac{5}{18}:\left(\dfrac{1}{15}+\dfrac{13}{12}\right)\)

    \(=\dfrac{23}{5}:\dfrac{23}{20}=\dfrac{20}{5}=4\)


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Summer Clouds
19/05/2017 at 09:03
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2
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The area of the square circumsribed in the semicircle is \(9cm^2\). If OC is the radius, find the area of the semicircle. Leave the answer in \(\pi\).
A B O C H

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    Phan Thanh Tinh Coordinator 19/05/2017 at 12:58

    The edge of the square is : \(\sqrt{9}=3\) (cm)

    Hence,the diagonal OH of the square or the radius of the semicircle is \(3\sqrt{2}\)cm.

    The area of the semicircle is : \(\dfrac{\left(3\sqrt{2}\right)^2\pi}{2}=9\pi\)(cm2)

    Selected by MathYouLike
  • ...
    Nguyễn Thị Thu Thủy 19/05/2017 at 20:35

    Summer Clouds

     The edge of the square is : 

    √9=39=3 (cm)

    Hence,the diagonal OH of the square or the radius of the semicircle is 3√232cm.

    The area of the semicircle is : (3√2)2π2=9π(32)2π2=9π(cm2)


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Kayasari Ryuunosuke Coordinator
20/07/2017 at 20:31
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Give x + y = 1. 

Find smallest value of F know :

F = x2 + y2 + xy 

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    Lufans 21/07/2017 at 20:21

    x + y = 1 <=> y = 1 - x

    We have: F = x2 + (1 - x)2 + (1 - x).x

                       = x2 + 1 + x2 - 2x + x - x2

                       = x2 - x + 1

                       \(=\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}\ge\dfrac{3}{4}\forall x\)

    Equal signs occur when and only of \(x-\dfrac{1}{2}=0\) \(\Leftrightarrow x=\dfrac{1}{2}\)

    \(y=1-\dfrac{1}{2}=\dfrac{1}{2}\)

    min A \(=\dfrac{1}{2}\Leftrightarrow x=y=\dfrac{1}{2}\)

    Selected by MathYouLike
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    keikoluong 20/07/2017 at 23:09

    x+y=1             \(\Rightarrow\)\(x^2+2xy+y^2=1\)\(\left(1\right)\)

    which \(\left(x-y\right)^2\ge0\)     else \(x^2-2xy+y^2\ge0\left(2\right)\)

    plus 1 and 2 we have   \(2\left(x^2+y^2\right)\ge1\Rightarrow x^2+y^2\ge\dfrac{1}{2}\)

    minA=\(\dfrac{1}{2}\)      When and only when  x = y = \(\dfrac{1}{2}\)


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Summer Clouds moderators
08/08/2017 at 08:55
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The function y = 3x + 6 is graphed in the coordinate plane. At what point on the graph is the y-value double the x-value?

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    WhySoSerious 08/08/2017 at 14:35

    Because the y value double the x value so : \(y=2x\)

    So the function is equal \(2x=3x+6\)

    We get x = -6.

    So we get y = \(2\cdot\left(-6\right)=-12\)

    At the point \(\left(-6;-12\right)\)the y-value double the x-value.

    Selected by MathYouLike
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    Phan Thanh Tinh Coordinator 08/08/2017 at 18:10

    Let  \(\left(x_0;2x_0\right)\) be the coordinates of the point. Since the point belongs to the graph of the function y = 3x + 6,we have :

    \(2x_0=3x_0+6\Leftrightarrow x_0=-6\Leftrightarrow2x_0=-12\)

    So,the satisfied point is (-6 ; -12)


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Phan Huy Toàn
16/08/2017 at 15:44
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3
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Given two positive real numbers x,y so that x+y≥10x+y≥10 

Find the smallest value of P , know P = 2x+y+30/x+5/y

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    Kaya Renger Coordinator 16/08/2017 at 15:49

    Apply Cauchy inequality , we have :

    \(P=2x+y+\dfrac{30}{x}+\dfrac{5}{y}=\dfrac{4}{5}\left(x+y\right)+\left(\dfrac{6x}{5}+\dfrac{30}{x}\right)+\left(\dfrac{y}{5}+\dfrac{5}{y}\right)\)

    \(P\ge\dfrac{4}{5}.10+2.\sqrt{\dfrac{6x}{5}.\dfrac{30}{x}}+2.\sqrt{\dfrac{y}{5}.\dfrac{5}{y}}=8+6+2=16\)

    So \(Min_P=16\)

    <=> x = y = 5

    Selected by MathYouLike
  • ...
    Kaya Renger Coordinator 16/08/2017 at 15:52

    That is my question ok : https://e-learning.codienhanoi.edu.vn/questions/1902.html

    Searching before asking , ok cheater :V

  • ...
    Help you solve math 16/08/2017 at 15:54

    P=4/5(x+y)+(6/5x+30/x)+(y/5+5/y)≥45.10+2√6/5x.30/x+2√y/5.5/y

    =8+12+2=22=8+12+2=22

    minP=22⇔x=y=5⇔x=y=5

    haha


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Lê Quốc Trần Anh Coordinator
30/08/2017 at 16:57
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1
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Prove that:

\(x^2+2x+3⋮x+1\)

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    Dao Trong Luan 30/08/2017 at 17:42

    \(x^2+2x+3\)

    \(=x^2+2x+1+2\)

    \(=\left(x+1\right)^2+2\)

    We have:

    \(\left(x+1\right)^2⋮x+1\)

    \(\Rightarrow2⋮x+1\)

    \(\Rightarrow x+1\in\left\{\pm1;\pm2\right\}\)

    \(\Rightarrow x\in\left\{-2;0;-3;1\right\}\)

    So when x = -2; x = 0; x = -3 or x = 1 

    => \(x^2+2x+3⋮x+1\)

    The word "Prove that" is wrong

    Lê Quốc Trần Anh selected this answer.

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Summer Clouds moderators
15/09/2017 at 08:51
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3
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Using pennies, nickels, dimes and quarters, how many ways can you make 67 cents?

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    →இے๖ۣۜBoy™†hïếuGîa 16/09/2017 at 13:38

    Let p, n, d, q be the number of pennies, nickels, dimes, quarters we need to make 67 cents respectively (p,n,d,q∈Z+p,n,d,q∈Z+), then p + 5n + 10d + 25q = 67

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    Phan Minh Anh 20/09/2017 at 11:57

    The answer is 13

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    Phan Thanh Tinh Coordinator 15/09/2017 at 09:49

    Let p, n, d, q be the number of pennies, nickels, dimes, quarters we need to make 67 cents respectively (\(p,n,d,q\in Z^+\)), then p + 5n + 10d + 25q = 67

    We have :

    (q ; d ; n ; p) = (2 ; 1 ; 1 ; 2) ; (1 ; 3 ; 2 ; 2) ; (1 ; 3 ; 1 ; 7) ; 

    (1 ; 2 ; 4 ; 2) ; (1 ; 2 ; 3 ; 7) ; (1 ; 2 ; 2 ; 12) ; (1 ; 2 ; 1 ; 17)

    (1 ; 1 ; 6 ; 2) ; (1 ; 1 ; 5 ; 7) ; (1 ; 1 ; 4 ; 12) ; (1 ; 1 ; 3 ; 17) ;

    (1 ; 1 ; 2 ; 22) ; (1 ; 1 ; 1 ; 27)

    So, the answer is 13


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Trigonometric
sin cos tan cot sinh cosh tanh
Lim-log

Combined operations

 

α β γ δ θ σ ∂ ε ω φ ϕ π μ λ Ψ ξ η χ ζ ι κ ν ψ Ω ρ τ υ Γ Δ Λ Φ Π Σ Υ Ξ ϑ Θ ς ϰ
∞ ⊻ ⩞ ⋎ ⋏ ≀ ∪ ⊎ ⋓ ∩ ⋒ ⊔ ⊓ ⨿ ⊗ ⊙ ⊚ ⊛ ⊘ ⊝ ⊕ ⊖ ⊠ ◯ ⊥
⇔ ⇒ ⇐ → ← ↔ ↑ ↓
Operations
+ - ÷ × ≠ = ⊂ ⊃ ⊆ ⊇ ≈ ∈ ∉ ∃ ∄ ≤ ≥ ± ∓ ≠ ∅ ≃ ≅ ≡ ⋮ ⋮̸ ∀
(□) [□] {□} |□|

The type of system

m×n 1×2 1×3 1×4 1×5 1×6
2×1 2×2 2×3 2×4 2×5 2×6
3×1 3×2 3×3 3×4 3×5 3×6
4×1 4×2 4×3 4×4 4×5 4×6
5×1 5×2 5×3 5×4 5×5 5×6
6×1 6×2 6×3 6×4 6×5 6×6

Recipe:

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