sai vì 1ha = 10000 m²

\(\left(-\dfrac{5}{11}:\dfrac{13}{8}-\dfrac{5}{11}:\dfrac{13}{5}\right)+\dfrac{-1}{33}\)

\(=\left(-\dfrac{5}{11}\times\dfrac{8}{13}-\dfrac{5}{11}\times\dfrac{5}{13}\right)-\dfrac{1}{33}\)

\(=\left(-\dfrac{5}{11}\times\left(\dfrac{8}{13}+\dfrac{5}{13}\right)\right)-\dfrac{1}{33}\)

\(=\left(-\dfrac{5}{11}\times\dfrac{13}{13}\right)-\dfrac{1}{33}\)

\(=-\dfrac{5}{11}-\dfrac{1}{33}\)

\(=-\dfrac{15}{33}-\dfrac{1}{33}=-\dfrac{16}{33}\)

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B2:

a, \(23-70-23+70+6=23\times\left(70-70\right)+6=23\times0+6=6\)

b, \(334-\left(45+334\right)-55=334-45-334-55=-100\)

B3:

a, \(\left(45-34\right)+\left(34-10\right)+5=45-34+34-10+5=40\)

b, \(\left(56-30\right)-\left(56+30\right)-40=56-30-56-30-40=-100\)

\(3-2\sqrt{x}=-1\)

\(\Leftrightarrow-2\sqrt{x}=-4\)

\(\Leftrightarrow\sqrt{x}=2\)

\(\Leftrightarrow x=4\)

\(18\times43+58\times18-18=18\times\left(43+58-1\right)=18\times100=1800\)

\(\Rightarrow B\)

\(\dfrac{1}{3}m^2+\dfrac{1}{3}m^2+1\dfrac{1}{3}m^2=\dfrac{1}{3}m^2+\dfrac{1}{3}m^2+\dfrac{4}{3}m^2=\left(\dfrac{1}{3}+\dfrac{1}{3}+\dfrac{4}{3}\right)m^2=\dfrac{6}{3}m^2=2m^2\)