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a) \(x+1,23\div3=1,845\) c) Không rõ
\(x+0,41=1,845\)
\(x=1,845-0,41\)
\(x=1,435\)
b) \(x\times\frac{1}{4}+x\times\frac{1}{5}+x\times2=19,6\) d) \(x+3\frac{1}{2}+20=24\frac{1}{4}\)
\(x\times\left(\frac{1}{4}+\frac{1}{5}+2\right)=19,6\) \(x+\frac{7}{2}+20=\frac{97}{4}\)
\(x\times\frac{49}{20}=19,6\) \(x+\frac{47}{2}=\frac{97}{4}\)
\(x=19,6\div\frac{49}{20}\) \(x=\frac{97}{4}\div\frac{47}{2}\)
\(x=8\) \(x=\frac{97}{94}\)
b, \(x\)x \(\frac{1}{4}\)+ \(x\)x \(\frac{1}{5}\)+ \(x\)x 2 = 19,6
\(x\)x (\(\frac{1}{4}+\frac{1}{5}+2\)) = 19,6
\(x\)x\(\frac{49}{20}\)= 19,6
\(x\) = \(19,6:\frac{49}{20}\)
\(x=8\)
\(B=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1-\dfrac{1}{4}\right)...\left(1-\dfrac{1}{2004}\right)\)
\(B=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot...\cdot\dfrac{2003}{2004}\)
\(B=\dfrac{1\cdot2\cdot3\cdot...\cdot2003}{2\cdot3\cdot4\cdot...\cdot2004}\)
\(B=\dfrac{1}{2004}\)
B=(1-1/2)x(1-1/3)x(1-1/4)x(1-1/5)...(1-1/2003)x(1-1/2004)
B=1/2x2/3x3/4x4/5x...x2002/2003x2003/2004
B=1/2004
a) Ta có:
1; 4; 7;...; 100 có (100 - 1) : 3 + 1 = 34 (số)
1 + 4 + 7+ ... + 100 = (100 + 1) × 34 : 2
= 101 × 17
(1 + 4 + 7 + ... + 100) : a = 17
101 × 17 : a = 17
a = 101 × 17 : 17
a = 100
b) (X - 1/2) × 5/3 = 7/4 - 1/2
(X - 1/2) × 5/3 = 5/4
X - 1/2 = 5/4 : 5/3
X - 1/2 = 3/4
X = 3/4 + 1/2
X = 5/4
a) (1 + 4 + 7 +...+ 100) : a = 17
1717 : a = 17
a = 101
b) \(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{7}{4}-\dfrac{1}{2}\)
\(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{10}{8}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\div\dfrac{5}{3}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\times\dfrac{3}{5}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{3}{4}\)
\(x-\dfrac{1}{2}=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}+\dfrac{1}{2}\)
\(x=\dfrac{5}{4}\)