Bài 1)
-17/35
Bài 2)
x +2 = -2/7 x 1/5
x+2 = -2/35
x = -2/35 - 2
x = -72/35
B1
\(\left(-\dfrac{3}{7}-\dfrac{6}{7}\right)+\dfrac{4}{5}=-\dfrac{9}{7}+\dfrac{4}{5}=\dfrac{-45}{35}+\dfrac{28}{35}=\dfrac{-17}{35}\)
B2
x+2=\(-\dfrac{2}{7}\times\dfrac{1}{5}\)
x+2=\(-\dfrac{2}{35}\)
x=\(-\dfrac{2}{35}-2\)
x=\(-\dfrac{72}{35}\)
Bài 1:
\(-\dfrac{3}{7}+\dfrac{4}{5}+\dfrac{6}{7}=\left(-\dfrac{3}{7}+\dfrac{6}{7}\right)+\dfrac{4}{5}=\dfrac{3}{7}+\dfrac{4}{5}=\dfrac{15}{35}+\dfrac{28}{35}=\dfrac{43}{35}\)
Bài 2:
\(\left(x+2\right):\dfrac{1}{5}=-\dfrac{2}{7}\)
\(x+2=-\dfrac{2}{7}\times\dfrac{1}{5}\)
\(x+2=-\dfrac{2}{35}\)
\(x=-\dfrac{2}{35}-2\)
\(x=-\dfrac{72}{35}\)
\(1,-\dfrac{3}{7}+\dfrac{4}{5}+\dfrac{-6}{7}=-\dfrac{15}{35}+\dfrac{28}{35}+\dfrac{-30}{35}=\dfrac{-15+28-30}{35}=-\dfrac{17}{35}\)
\(2,\left(x+2\right):\dfrac{1}{5}=-\dfrac{2}{7}\)
\(\Leftrightarrow x+2=-\dfrac{2}{7}.\dfrac{1}{5}\)
\(\Leftrightarrow x+2=-\dfrac{2}{35}\)
\(\Leftrightarrow x=-\dfrac{2}{35}-2\)
\(\Leftrightarrow x=-\dfrac{2}{35}-\dfrac{70}{35}\)
\(\Leftrightarrow x=-\dfrac{72}{35}\)