\(\dfrac{1}{\left(x+1\right)\left(x+2\right)}+\dfrac{1}{\left(x+2\right)\left(x+3\right)}+\dfrac{1}{\left(x+3\right)\left(x+4\right)}=\dfrac{2019}{2020}\)

\(\Leftrightarrow\dfrac{1}{x+1}-\dfrac{1}{x+2}+\dfrac{1}{x+2}-\dfrac{1}{x+3}+\dfrac{1}{x+3}-\dfrac{1}{x+4}=\dfrac{2019}{2020}\)

\(\Leftrightarrow\dfrac{1}{x+1}-\dfrac{1}{x+4}=\dfrac{2019}{2020}\)

\(\Leftrightarrow\dfrac{x+4-x-1}{\left(x+1\right)\left(x+4\right)}=\dfrac{2019}{2020}\)

\(\Leftrightarrow\dfrac{3}{\left(x+1\right)\left(x+4\right)}=\dfrac{2019}{2020}\)

\(\Leftrightarrow\left(x+1\right)\left(x+4\right).2019=6060\)

<=> x = - 0,208387929

P/s: Số lạ zậy?Đề sai ko

6060 nha bạn

a, \(=\dfrac{1.2.3...5}{2.3...6}=\dfrac{1}{6}\)

C

C

C

\(A=\left(2020\times2019+2019\times2018\right)\times\left(1+\dfrac{1}{2}:1\dfrac{1}{2}-1\dfrac{1}{3}\right)\)

\(A=\left[2019\times\left(2020+2018\right)\right]\times\left(1+\dfrac{1}{2}:\dfrac{3}{2}-\dfrac{4}{3}\right)\)

\(A=4038\times2019\times\left(1+\dfrac{1}{3}-\dfrac{4}{3}\right)\)

\(A=4038\times2019\times0\)

\(A=0\)

a) (x - 1)³ - 1 = 0

<=> (x - 1)³ = 0 + 1

<=> (x - 1)³ = 1

<=> (x - 1)³ = 1³

<=> x - 1 = 1

<=> x = 1 + 1

<=> x = 2

=> x = 2

b) (x - 4)²⁰¹⁹ = 1

<=> (x - 4)²⁰¹⁹ = 1²⁰¹⁹

<=> x - 4 = 1

<=> x = 1 + 4

<=> x = 5

=> x = 5

c) (x - 2019)²⁰²⁰ = 0

<=> (x - 2019)²⁰²⁰ = 0²⁰²⁰

<=> x - 2019 = 0

<=> x = 0 + 2019

<=> x = 2019

=> x = 2019

d) (x - 1)² = (x - 1)³

<=> x² - 2x + 1 = x³ - 2x² + x - x² + 2x - 1

<=> x² - 2x + 1 = x³ - 3x² + 3 - 1

<=> x² - 2x + 1 - x³ + 3x² - 3 + 1 = 0

<=> 4x² - 5x + 2 - x³ = 0

<=> (-x² + 3x - 2)(x - 1) = 0

<=> (x² - 3x + 2)(x - 1) = 0

<=> (x - 2)(x - 1)(x - 1) = 0

<=> x - 2 = 0 hoặc x - 1 = 0

       x = 0 + 2         x = 0 + 1

       x = 2               x = 1

=> x = 1 hoặc x = 2

\(a.=\dfrac{2019}{2020}\times\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)\\ =\dfrac{2019}{2020}\times1=\dfrac{2019}{2020}\\ b.=\dfrac{25}{27}\times\left(\dfrac{17}{14}-\dfrac{1}{14}-\dfrac{2}{14}\right)\\ =\dfrac{25}{27}\times1=\dfrac{25}{27}\)

Thanks mik chữ cũng hơi ẩu

Dễ thấy A chia hết cho 10 nên A có tận cùng là 0

còn 1x 3 x 5 x... x 2021 là một số lẻ và chia hết cho 5 nên có tận cùng là 5

Là 1 bạn ơi!!!

gt&#x21D2;x2&#x2212;xy&#x2212;(5x&#x2212;5y)&#x2212;x+8=0&#x21D2;(x&#x2212;y)(x&#x2212;5)&#x2212;(x&#x2212;5)=&#x2212;3&#x21D2;(5&#x2212;x)(x&#x2212;y&#x2212;1)=3" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal" class="MathJax_CHTML mjx-chtml">gt⇒x2−xy−(5x−5y)−x+8=0⇒(x−y)(x−5)−(x−5)=−3⇒(5−x)(x−y−1)=3

3" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal" class="MathJax_CHTML mjx-chtml">3 là sẽ tìm được nghiệm nguyên của PT