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a) \(\frac{x}{2}=\frac{y}{5}=\frac{z}{4}\)
Áp dụng tính chất dãy tỉ số bằng nhau , ta có:
\(\frac{x}{2}=\frac{y}{5}=\frac{z}{4}=\frac{2x}{4}=\frac{3y}{15}=\frac{z}{4}=\frac{2x-3y+z}{4-15+4}=\frac{112}{7}=16\)
\(\frac{x}{2}=16=>x=32\)
\(\frac{y}{5}=16=>x=80\)
\(\frac{z}{4}=16=>z=64\)
Câu b) tương tự chỉ cần thay số vào nha bạn
Ta có:
\(A=\frac{112}{13.20}+\frac{112}{20.27}+.........+\frac{112}{62.69}\)
\(\Rightarrow A=112.\left(\frac{1}{13.20}+\frac{1}{20.27}+..........+\frac{1}{62.69}\right)\)
\(\Rightarrow A=16.\left(\frac{7}{13.20}+\frac{7}{20.27}+.......+\frac{7}{62.69}\right)\)
\(\Rightarrow A=16.\left(\frac{1}{13}-\frac{1}{20}+\frac{1}{20}-\frac{1}{27}+........+\frac{1}{62}-\frac{1}{69}\right)\)
\(\Rightarrow A=16.\left(\frac{1}{13}-\frac{1}{69}\right)\)
\(\Rightarrow A=16.\frac{56}{897}\)
\(\Rightarrow A=\frac{896}{897}\)
Vậy: \(A=\frac{896}{897}\)
\(A=\frac{112}{13.20}+\frac{112}{20.27}+\frac{112}{27.34}+...+\frac{112}{62.69}\)
\(\Rightarrow A=112.\left(\frac{1}{13.20}+\frac{1}{20.27}+\frac{1}{27.34}+...+\frac{1}{62.69}\right)\)
\(\Rightarrow A=112.\frac{7}{7}.\left(\frac{1}{13.20}+\frac{1}{20.27}+\frac{1}{27.34}+...+\frac{1}{62.69}\right)\)
\(\Rightarrow A=112.\frac{1}{7}\left(\frac{7}{13.20}+\frac{7}{20.27}+\frac{7}{27.34}+...+\frac{7}{62.69}\right)\)
\(\Rightarrow A=16\left(\frac{1}{13}-\frac{1}{20}+\frac{1}{20}-\frac{1}{27}+\frac{1}{27}-\frac{1}{34}+...+\frac{1}{62}-\frac{1}{69}\right)\)
\(\Rightarrow A=16\left(\frac{1}{13}-\frac{1}{69}\right)\)
\(\Rightarrow A=16.\frac{56}{897}\)
\(\Rightarrow A=\frac{896}{897}\)
\(Can\)\(you\) \(k\) \(for\) \(me,everyone?\)
