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\(\frac{x-2}{2017}+\frac{x-3}{2018}=\frac{x-4}{2019}+\frac{x-5}{2020}\)
<=> \(\frac{x-2}{2017}+1+\frac{x-3}{2018}+1=\frac{x-4}{2019}+1+\frac{x-5}{2020}+1\)
<=> \(\frac{x+2015}{2017}+\frac{x+2015}{2018}-\frac{x+2015}{2019}-\frac{x+2015}{2020}=0\)
<=> \(\left(x+2015\right)\left(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}\right)=0\)
<=> x + 2015 = 0 ( vì \(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}\ne0\))
<=> x = - 2015
Vậy x = -2015.
Giải phương trình :
\(\frac{x-2}{2017}+\frac{x-3}{2018}=\frac{x-4}{2019}+\frac{x-5}{2020}\)
\(\Rightarrow\frac{x-2}{2017}+1+\frac{x-3}{2018}+1=\frac{x-4}{2019}+1+\frac{x-5}{2020}+1\)
\(\Rightarrow\frac{x+2015}{2017}+\frac{x+2015}{2018}-\frac{x+2015}{2019}-\frac{x+2015}{2020}=0\)
\(\Rightarrow\left(x+2015\right)\left(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}\right)=0\)
Mà \(\left(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}\right)>0\)
\(\Rightarrow x+2015=0\)
\(\Rightarrow x=-2015\)
Đề: \(\frac{x-2}{2020}+\frac{x-3}{2019}=\frac{x-4}{2018}+\frac{x-5}{2017}\)
⇔ \(\left(\frac{x-2}{2020}-1\right)+\left(\frac{x-3}{2019}-1\right)=\left(\frac{x-4}{2018}-1\right)+\left(\frac{x-5}{2017}-1\right)\)
⇔ \(\frac{x-2022}{2020}+\frac{x-2022}{2019}=\frac{x-2022}{2018}+\frac{x-2022}{2017}\)
⇔\(\frac{x-2022}{2020}+\frac{x-2022}{2019}-\frac{x-2022}{2018}-\frac{x-2022}{2017}=0\)
⇔ \(\left(x-2022\right)\)\(\left(\frac{1}{2020}+\frac{1}{2019}-\frac{1}{2018}-\frac{1}{2017}\right)\) = 0
Nên x - 2022 = 0 ⇔ x = 2022
Mà \(\left(\frac{1}{2020}+\frac{1}{2019}-\frac{1}{2018}-\frac{1}{2017}\right)\)≠0
Vậy nghiệm của pt là x = 2022
= ( 2 + 22 + 23) + ( 24 + 25 + 26) + ............ + (22017 + 22018 + 22019) \(⋮\)7
= 2.( 1 + 2 + 22 ) + 24 (1 + 2 + 22) +..................+ 22017.( 1 + 2 + 22) \(⋮\)7
=( 2. 7 + 24.7 +.............+ 22017.7 ) \(⋮\)7
= 7 . ( 2 + 24 + ..... + 22017) \(⋮\)7
Vâỵ : ....................................................... \(⋮\)7
\(\dfrac{x+1}{2020}+\dfrac{x+2}{2019}+\dfrac{x+3}{2018}+\dfrac{x+4}{2017}+4=0\)
⇔ \(\dfrac{x+1}{2020}+1+\dfrac{x+2}{2019}+1+\dfrac{x+3}{2018}+1+\dfrac{x+4}{2017}+1=0\)
\(\Leftrightarrow\) \(\dfrac{x+2021}{2020}+\dfrac{x+2021}{2019}+\dfrac{x+2021}{2018}+\dfrac{x+2021}{2017}=0\)
⇔ \(\left(x+2021\right)\left(\dfrac{1}{2020}+\dfrac{1}{2019}+\dfrac{1}{2018}+\dfrac{1}{2017}\right)=0\)
\(Do\) \(\left(\dfrac{1}{2020}+\dfrac{1}{2019}+\dfrac{1}{2018}+\dfrac{1}{2017}\right)\ne0\)
⇒ \(x+2021=0\)
⇔ \(x=-2021\)
\(Vậy\) \(x=-2021\)
Câu hỏi của Thị Kim Vĩnh Bùi - Toán lớp 8 - Học toán với OnlineMath
Ở link trên đã tìm đc các giá trị của a, b, c, d thay vào tìm đc M = 0.
Ta có:\(\frac{x-2}{2017}+1+\frac{x-3}{2018}+1=\frac{x-4}{2019}+1+\frac{x-5}{2020}+1\)
\(\Rightarrow\frac{x+2015}{2017}+\frac{x+2015}{2018}-\frac{x+2015}{2019}-\frac{x+2015}{2020}=0\)
\(\Rightarrow\left(x+2015\right)\left(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}\right)=0\)
Mà \(\frac{1}{2017}+\frac{1}{2018}-\frac{1}{2019}-\frac{1}{2020}>0\)
\(\Rightarrow x+2015=0\Rightarrow x=-2015\)
\(S=\left\{-2015\right\}\)
\(M=2.3.4.4+3.4.5.4+...+2018.2019.2020.4\)
\(M=2.3.4.\left(5-1\right)+3.4.5.\left(6-2\right)+...+2018.2019.2020.\left(2021-2017\right)\)
M=2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+...+2018.2019.2020.2021-2017.2018.2019.2020=2018.2019.2020-1.2.3.4
Vì \(x=2018\Rightarrow x+1=2019\)
Thay x+1=2019 vào biểu thức A ta được :
\(A=x^6-\left(x+1\right)x^5+\left(x+1\right)x^4-...-\left(x+1\right)x+x+1\)
\(=x^6-x^6-x^5+x^5+x^4-...-x^2-x+x+1\)
\(=1\)
\(A=x^6-2019x^5+2018x^4-2019x^3+2019x^2-2019x+2019\)
\(=x^6-2018x^5-x^5+2018x^4+x^4-2018x^3-x^3+2018x^2+x^2\)
\(-2018x-x+2019\)
\(=x^5\left(x-2018\right)-x^4\left(x-2018\right)-x^3\left(x-2018\right)+x^2\left(x-2018\right)\)
\(+x\left(x-2018\right)-\left(x-2018\right)+1\)
= 1
