1.\(=56+47-56+53-40\)
\(=\left(56-56\right)+\left(47+53\right)-40\)
\(=0+100-40=60\)
2.\(34+59-34+41+100\)
\(=\left(34-34\right)+\left(59+41\right)+100\)
\(=0+100+100=200\)
3.\(=109+34-109+66-10\)
\(=\left(109-109\right)+\left(34+66\right)-10\)
\(=0+100-10=90\)

  56 x 17 + 56 x 24 +41 x 44  

= 56 x ( 17 + 24 ) + 41 x 44

= 56 x 41 + 41 x 44

= ( 56 + 44 ) x 44

= 100 x 44

= 4400

290

290

290

\(-56+\left|-x+23\right|=-41\)

\(\Leftrightarrow-56+\left|23-x\right|=-41\)

\(\Leftrightarrow\left|23-x\right|-56=-41\)

\(\Leftrightarrow\left|23-x\right|=15\)

\(\Leftrightarrow\orbr{\begin{cases}23-x=15\\23-x=-15\end{cases}\Leftrightarrow\orbr{\begin{cases}x=8\\x=38\end{cases}}}\)

Vậy \(x\in\left\{8;38\right\}\)

-56+|-x+23|=-41

        |-x+23|=-41- (-56)

        |-x+23|=-41+56

        |-x+23|=15

      =>  \(\orbr{\begin{cases}-x+23=15\\-x+23=-15\end{cases}}\)

      =>\(\orbr{\begin{cases}-x=15-23\\-x=-15-23\end{cases}}\)

      =>\(\orbr{\begin{cases}-x=-8\\-x=-38\end{cases}}\)

=>\(\orbr{\begin{cases}x=8\\x=38\end{cases}}\)

   –23  chia hết cho  x –  2

\(=1-\dfrac{1}{2}+1-\dfrac{1}{6}+...+1-\dfrac{1}{90}\)

\(=10-\left(\dfrac{1}{2}+\dfrac{1}{6}+...+\dfrac{1}{90}\right)\)

\(=10-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)\)

=9+1/10

=9,1

( 2055 + 300 ) x 56 - 699

= 2355 x 56 - 699

= 131880 - 699

= 131181

( 2055+300)* 56-699 =131181

\(23+23-11=22+23-10\)

\(56+21-15=21+56-15\)

\(44+44-22>46+41-26\)

\(23+23-11>22+22-10\)

\(56+21-15=21+56-15\)

\(44+44-22>46+41-26\)

Câu kia sai đừng k 

23+23-11 = 22+22-10

56+21-15 = 21+56-15

44+44-22 < 46+41-26

23 + 23 - 11 > 22 + 22 -10

56 + 21 - 15 = 21 + 56 - 15

44 + 44 - 22 > 46 + 41 - 26

23 + 23 -11 > 22 + 22 - 10

56 + 21 - 11 = 21 + 56 - 15 

44 + 44 - 22  >  46 + 41 - 26