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Bài 1:
a) \(\frac{-5}{21}+\frac{-2}{21}+\frac{8}{24} \)
\(=\frac{-7}{21}+\frac{1}{3}\)
\(=\frac{-1}{3}+\frac{1}{3}\)
\(=0\)
b) \(\frac{-3}{5}.\frac{2}{7}+\frac{-3}{5}.\frac{5}{7}+2\frac{3}{5}\)
\(=\frac{-3}{5}.\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{13}{5}\)
\(=\frac{-3}{5}.1+\frac{13}{5}\)
\(=\frac{-3}{5}+\frac{13}{5}\)
\(=\frac{10}{5}\)
\(=2\)
c) \(75\%-1\frac{1}{2}+0,5\div\frac{5}{12}-\left(-\frac{1}{2}\right)^2\)
\(=\frac{3}{4}-\frac{3}{2}+\frac{1}{2}.\frac{12}{5}-\frac{1}{4}\)
\(=\frac{3}{4}-\frac{3}{2}+\frac{6}{5}-\frac{1}{4}\)
\(=\frac{3}{4}+\frac{-3}{2}+\frac{6}{5}+\frac{-1}{4}\)
\(=\left(\frac{3}{4}+\frac{-1}{4}\right)+\frac{-3}{2}+\frac{6}{5}\)
\(=\frac{1}{2}+\frac{-3}{2}+\frac{6}{5}\)
\(=-1+\frac{6}{5}\)
\(=\frac{-5}{5}+\frac{6}{5}\)
\(=\frac{1}{5}\)
Bài 2:
a) \(1\frac{1}{3}+\frac{2}{3}x=5\frac{1}{3}\)
\(\frac{4}{3}+\frac{2}{3}x=\frac{16}{3}\)
\(\frac{2}{3}x=\frac{16}{3}-\frac{4}{3}\)
\(\frac{2}{3}x=4\)
\(x=4\div\frac{2}{3}\)
\(x=4.\frac{3}{2}\)
\(x=6\)
Vậy \(x=6\)
b) \(\left(x+\frac{1}{3}\right)\left(\frac{3}{4}-2x\right)=0\)
TH1: \(x+\frac{1}{3}=0\)
\(x=0-\frac{1}{3}\)
\(x=\frac{-1}{3}\)
TH2 : \(\frac{3}{4}-2x=0\)
\(2x=\frac{3}{4}-0\)
\(2x=\frac{3}{4}\)
\(x=\frac{3}{4}\div2\)
\(x=\frac{3}{4}.\frac{1}{2}\)
\(x=\frac{3}{8}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{-1}{3}\\x=\frac{3}{8}\end{cases}}\)
c) \(\frac{-4}{5}x+1\frac{1}{3}x=-1\frac{1}{3}\)
\(\frac{-4}{5}x+\frac{4}{3}x=\frac{-4}{3}\)
\(\left(\frac{-4}{5}+\frac{4}{3}\right).x=\frac{-4}{3}\)
\(\frac{8}{15}.x=\frac{-4}{3}\)
\(x=\frac{-4}{3}\div\frac{8}{15}\)
\(x=\frac{-4}{3}.\frac{15}{8}\)
\(x=\frac{-5}{2}\)
Vậy \(x=\frac{-5}{2}\)
Câu 1:
10 000 000 000 000 000 000 000+1=10 000 000 000 000 000 000 001.
Chúc học tốt!
1−3−9+13+17−21−25+...−393+397+4011−5−9+13+17−21−25+...−393+397+401
=(1−3−9+13)+(17−21−25+29)+...+(385−389−393+397)+401=(1−5−9+13)+(17−21−25+29)+...+(385−389−393+397)+401
=0+0+...+0+401=401
