5 : 2.5 ; 26 : 6.5 ; 7 : 17.5 ; 459 : 6.8 .
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Những câu hỏi liên quan
12 :{390:[2.5^2-(5^3+7^2.5)]}
1.3.5.7...99=5/2.5/2.5/2...100/2
Tim x
2.5^2.3^2+{[2.5^3-(5x+4).5]}:(262.3.5)}=453
5²x-³ - 2.5² = 5² . 3
Cho 3.5, 3^2.5, 3^2.5^2, ..., 3^n.5^k . hỏi có bao nhiêu ước số chung?
5+2.5+5+3.5+...+5+9.5=
5+2.5+3.5+...+8.5+9.5
=5.(1+2+3+...+8+9)
=5.\(\frac{\left(9+1\right).9}{2}\)
=5.45
=225
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5/2.5 + 5/5.8 + 5/8.11 + ... + 5/ 98.101 = ?
\(\frac{5}{2.5}+\frac{5}{5.8}+......+\frac{5}{98.101}\)
\(=\frac{5}{3}.\left(\frac{3}{2.5}+\frac{3}{5.8}+.........+\frac{3}{98.101}\right)\)
\(=\frac{5}{3}.\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+........+\frac{1}{98}-\frac{1}{101}\right)\)
\(=\frac{5}{3}.\left(\frac{1}{2}-\frac{1}{101}\right)=\frac{5}{3}.\frac{99}{202}\)
\(=\frac{5.33}{202}=\frac{165}{202}\)
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5^2.5^7+5^12=?
5^2x-3-2.5^2=5^2.3
\(5^{2x-3}-2\cdot5^2=5^2\cdot3\)
\(\Rightarrow5^{2x-3}-50=75\)
\(\Rightarrow5^{2x-3}=75+50\)
\(\Rightarrow5^{2x-3}=125\)
\(\Rightarrow5^{2x-3}=5^3\)
\(\Rightarrow2x-3=3\)
\(\Rightarrow2x=6\)
\(\Rightarrow x=\dfrac{6}{2}=3\)
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5^2x-3-2.5^2=5^2.3
\(5^{2x-3}-2.5^2=5^2.3\)
\(5^{2x-3}=2.5^2+5^2.3\)
\(2x-3=3\)
\(2x=3+3\)
\(2x=6\)
\(x=6:2=3\)
\(\Rightarrow x=3\)
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