Bài 1: Tính ( hợp lý nếu có thể)
A=\(\dfrac{-3}{8}\)+\(\dfrac{12}{25}\)+\(\dfrac{5}{-8}\)+\(\dfrac{2}{-5}\)+\(\dfrac{13}{25}\)
B=\(\dfrac{-3}{15}\)+(\(\dfrac{2}{3}\)+\(\dfrac{3}{15}\))
C=\(\dfrac{-5}{21}\)+(\(\dfrac{-16}{21}\)+1)
D=(\(\dfrac{-1}{6}\)+\(\dfrac{5}{-12}\))+\(\dfrac{7}{12}\)
E=\(\dfrac{1}{3}\)x\(\dfrac{4}{5}\)+\(\dfrac{1}{3}\)x\(\dfrac{6}{5}\)+\(\dfrac{2}{3}\)
F=\(\dfrac{-5}{6}\)x\(\dfrac{4}{19}\)+\(\dfrac{-7}{12}\)x\(\dfrac{4}{12}\)-\(\dfrac{40}{47}\)
Bài 2: Tìm x,biết:
a) x + \(\dfrac{2}{3}\) = \(\dfrac{4}{5}\)
b) x - \(\dfrac{2}{3}\) = \(\dfrac{7}{21}\)
c) -x - \(\dfrac{3}{4}\) =\(\dfrac{-8}{11}\)
d) \(\dfrac{11}{12}\) - (\(\dfrac{2}{5}\) + x) = \(\dfrac{2}{3}\)
Bài 1: Tính ( hợp lý nếu có thể )
\(A=\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)
\(=\left(\dfrac{-3}{8}+\dfrac{5}{-8}\right)+\left(\dfrac{12}{25}+\dfrac{13}{25}\right)+\dfrac{2}{-5}\)
\(=-1+1+\dfrac{2}{-5}\)
\(=0+\dfrac{2}{-5}\)
\(=\dfrac{2}{-5}\)
\(B=\dfrac{-3}{15}+\left(\dfrac{2}{3}+\dfrac{3}{15}\right)\)
\(=\left(\dfrac{-3}{15}+\dfrac{3}{15}\right)+\dfrac{2}{3}\)
\(=0+\dfrac{2}{3}\)
\(=\dfrac{2}{3}\)
\(C=\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
\(=\left(\dfrac{-5}{21}+\dfrac{-16}{21}\right)+1\)
\(=-1+1\)
\(=0\)
\(D=\left(\dfrac{-1}{6}+\dfrac{5}{-12}\right)+\dfrac{7}{12}\)
\(=\left(\dfrac{5}{-12}+\dfrac{7}{12}\right)+\dfrac{-1}{6}\)
\(=\dfrac{1}{6}+\dfrac{-1}{6}\)
\(=0\)
Bài 2: Tìm x,biết:
a) \(x+\dfrac{2}{3}=\dfrac{4}{5}\)
\(x=\dfrac{4}{5}-\dfrac{2}{3}\)
\(x=\dfrac{2}{15}\)
Vậy \(x=\dfrac{2}{15}\)
b) \(x-\dfrac{2}{3}=\dfrac{7}{21}\)
\(\Rightarrow x-\dfrac{2}{3}=\dfrac{1}{3}\)
\(x=\dfrac{1}{3}+\dfrac{2}{3}\)
\(x=\dfrac{3}{3}=1\)
Vậy \(x=1\)
c) sai đề hay sao ấy bạn.bỏ dấu - ở x thì đúng đề.mk giải luôn nha!
\(x-\dfrac{3}{4}=\dfrac{-8}{11}\)
\(x=\dfrac{-8}{11}+\dfrac{3}{4}\)
\(x=\dfrac{1}{44}\)
Vậy \(x=\dfrac{1}{44}\)
d) \(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}\)
\(\dfrac{2}{5}+x=\dfrac{1}{4}\)
\(x=\dfrac{1}{4}-\dfrac{2}{5}\)
\(x=-\dfrac{3}{20}\)
Vậy \(x=-\dfrac{3}{20}\)