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nè mình gợi ý cho gọi a= 1-1/2-1/2^2-1/2^3-......... ......1/2^2014 1 / 2^2>1 / 2.3 1/2^3>1/3.4 ................ 1/2^2014<1/2014.2015 nen 1-1/2-1/2^2-1/2^3-.........................1/^2014>1-1/1.2-1/2.3-1/3.4-........................1/2014.2015 a<1-[1-1/2015] a<1-2014/2015 a<1/2015
\(a)\frac{2}{3}x-\frac{1}{2}=\frac{5}{12}\)
\(\Rightarrow\frac{2}{3}x=\frac{5}{12}+\frac{1}{2}=\frac{11}{12}\)
\(\Rightarrow x=\frac{11}{12}:\frac{2}{3}=\frac{11}{8}\)
\(b)\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)
\(\Rightarrow\frac{14}{5}x-50=51.\frac{2}{3}=34\)
\(\Rightarrow\frac{14}{5}x=34+50=84\)
\(\Rightarrow x=84:\frac{14}{5}=30\)
a) 2/3.x - 1/2 = 5/12
2/3.x = 5/12 + 1/2
2/3.x = 11/12
x = 11/12 : 2/3
x = 11/8
b) \(\left(2\frac{4}{5}.x-50\right):\frac{2}{3}=51\)
\(\frac{14}{5}.x-50=51.\frac{2}{3}\)
\(\frac{14}{5}.x-50=34\)
\(\frac{14}{5}.x=34+50\)
\(\frac{14}{5}.x=84\)
\(x=84:\frac{14}{5}\)
\(x=30\)
a
\(5\frac{4}{7}:x+=13\)
\(\frac{39}{7}:x=13\)
\(x=\frac{39}{7}:13\)
\(x=\frac{3}{7}\)
\(\frac{4}{7}x=\frac{9}{8}-0,125\)
\(\frac{4}{7}x=1\)
\(x=1:\frac{4}{7}\)
\(x=\frac{7}{4}=1\frac{3}{4}\)
1) Tìm x
\(\frac{11}{2}.x+\frac{1}{3}.x=1\)
\(\Rightarrow x\left(\frac{11}{2}+\frac{1}{3}\right)=1\)
\(\Rightarrow x\left(\frac{33}{6}+\frac{2}{6}\right)=1\)
\(\Rightarrow x.\frac{35}{6}=1\)
\(\Rightarrow x=\frac{6}{35}\)
2) So sánh
\(\frac{59}{40}< \frac{50}{31}\)( cái này bạn quy đồng là ra, mik chỉ ghi kq, bạn tự tính )
3)\(\frac{1}{3}+\frac{4}{7}-\frac{5}{14}-\frac{1}{2}-\frac{2}{3}\)
\(=\left(\frac{1}{3}-\frac{2}{3}\right)+\left(\frac{4}{7}-\frac{5}{14}\right)-\frac{1}{2}\)
\(=-\frac{1}{3}+\frac{3}{14}-\frac{1}{2}\)
\(=-\frac{13}{21}\)
1)\(\frac{11}{2}.x+\frac{1}{3}.x=1\)
\(x.\left(\frac{11}{2}+\frac{1}{3}=1\right)\)
\(x.\frac{35}{6}=1\)
\(x=1:\frac{35}{6}\)
\(x=\frac{6}{35}\)
2) Ta có:
\(\frac{59}{40}=\frac{1829}{1240}\)
\(\frac{50}{31}=\frac{2000}{1240}\)
Vì \(2000>1829\Rightarrow\frac{2000}{1240}>\frac{1829}{1240}\Rightarrow\frac{50}{31}>\frac{59}{40}\)
3)\(\frac{1}{3}+\frac{4}{7}-\frac{5}{14}-\frac{1}{2}-\frac{2}{3}\)
\(=\left(\frac{1}{3}-\frac{2}{3}\right)+\left(\frac{4}{7}-\frac{5}{14}-\frac{1}{2}\right)\)
\(=-\frac{1}{3}+\left(\frac{8}{14}-\frac{5}{14}-\frac{7}{14}\right)\)
\(=\frac{-1}{3}+\frac{-4}{14}\)
\(=\frac{-1}{3}+\frac{-2}{7}\)
\(=\frac{-7}{21}+\frac{-6}{21}\)
\(=\frac{-13}{21}\)
Câu hỏi của Phạm Quốc Hải - Toán lớp 8 - Học toán với OnlineMath
Bỏ lần số 6 là ra 31 quả cam.
Ta có \(F=2F-F=2\left(1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+...+\frac{1}{2^{2022}}\right)-\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2022}}\right)\)
\(=2+1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{2021}}-1-\frac{1}{2}-\frac{1}{2^2}-..-\frac{1}{2^{2022}}\)
\(=2-\frac{1}{2^{2022}}\)