=(-1+2)-(3+4)-(5+6)-........-(2017+2018)

=1-7-11-........-4035

=-1009

 (a+2017)^2018+/b-2018/=0

vì ( a + 2017 )²⁰¹⁸ \(\ge\)0 ; | b - 2018 | \(\ge\)0

\(\Rightarrow\)( a + 2017 )²⁰¹⁸ + | b - 2018 | \(\ge\)0

Mà ( a + 2017 )²⁰¹⁸ + | b - 2018 | = 0

\(\Rightarrow\hept{\begin{cases}\left(a+2017\right)^{2018}=0\\\left|b-2018\right|=0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}a+2017=0\\b-2018=0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}a=-2017\\b=2018\end{cases}}\)

Vì (a+2017)^2018 >= 0 và |b-2018| >= 0 nên VT >= 0

=> Để VT = 0 thì : a+2017=0 và b-2018=0 <=> a=-2017 và b=2018

Vậy a=-2017 và b=2018

Tk mk nha

\(\left(a+2017\right)^{2018}+|b-2018|=0\\\)Vì \(\left(a+2017\right)^{2018}\ge0;|b-2018|\ge0\)

\(\Rightarrow\left(a+2017\right)^{2018}+|b-2018|\ge0\)

Mà \(\left(a+2017\right)^{2018}+|b-2018|=0\)

\(\Rightarrow\hept{\begin{cases}\left(a+2017\right)^{2018}=0\\|b-2018|=0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}a+2017=0\\b-2018=0\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}a=-2017\\b=2018\end{cases}}\)

1991 + 2017 x 2016=1991 + 4066272=4068263

2018 + 2017 - 2034=4035 - 2034=2001

1991+2017 x 2016 = 1991 + 4066272

                               =  4068263

2018 + 2017 - 2043 = 4035 - 2014

                                 = 1992

k cho mk nha

`@` `\text {Ans}`

`\downarrow`

`a)`

`13/50 + 9% + 41/100 + 0,24`

`= 0,26 + 0,09 + 0,41 + 0,24`

`= (0,26 + 0,24) + (0,09 + 0,41)`

`= 0,5 + 0,5`

`= 1`

`b)`

`2018 \times 2020 - 1/2017 + 2018 \times 2019`

`= 2018 \times (2020 + 2019) - 1/2017`

`= 2018 \times 4039 - 1/2017`

`= 8150702`

`c)`

`1/2 + 1/6 + 1/12 + 1/20 +1/30 +1/42`

`=`\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)

`=`\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{6}-\dfrac{1}{7}\)

`=`\(1-\dfrac{1}{7}\)

`= 6/7`

\(a,\dfrac{13}{50}+9\%+\dfrac{41}{100}+0,24\\ 0,26+0,09+0,41+0,24\\ =\left(0,26+0,24\right)+\left(0,09+0,41\right)\\ =0,5+0,5\\ =1\\ b,2018\times2020-\dfrac{1}{2017}+2018\times2019\\ =2018\times\left(2020+2019\right)-\dfrac{1}{2017}\\ =2018\times4039-\dfrac{1}{2017}\\ =3150702-\dfrac{1}{2017}\\ c,\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\\ =1-\dfrac{1}{2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}.........+\dfrac{1}{6}-\dfrac{1}{7}\\ =1-\dfrac{1}{7}\\ =\dfrac{6}{7}\)

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