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c, (2\(\times\) \(x\) - 3) \(\times\) 5 = 4
2 \(\times\) \(x\) - 3 = \(\dfrac{4}{5}\)
2 \(\times\) \(x\) = 0,8 + 3
2\(x\) = 3,8
\(x\) = \(3,8\) : 2
\(x\) = 1,9
d, 1 + 3 + 5 +....+\(x\) = 36
(\(x\) + 1)\(\times\) \(x\): 2 = 36
(\(x+1\)) \(\times\)\(x\) = 72
(\(x+1\))\(\times\)\(x\) = 8 x 9
\(x\) = 8
a) (X - 5) x 4 = 36
⇒ X - 5 = 36 : 4
⇒ X - 5 = 9
⇒ X = 9 + 5
⇒ X = 14
Vậy X = 14
b) (48 - X) x 2 = 14
⇒ 48 - X = 14 : 2
⇒ 48 - X = 7
⇒ X = 48 - 7
⇒ X = 41
Vậy X = 41
\(B=\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}\)
\(=9.\left(\frac{4}{1.3.5}+\frac{4}{3.5.7}+\frac{4}{5.7.9}+...+\frac{4}{25.27.29}\right)\)
\(=9.\left(\frac{1}{1.3}-\frac{1}{3.5}+\frac{1}{3.5}-\frac{1}{5.7}+\frac{1}{5.7}-\frac{1}{7.9}+...+\frac{1}{25.27}-\frac{1}{27.29}\right)\)
\(=9.\left(\frac{1}{3}-\frac{1}{675}\right)\)
\(=9.\frac{224}{675}\)
\(=\frac{224}{75}\)
x-36/18+2.x+5=19+2.(x-1)
x-2+2x+5=19+2x-1.2
3x-2+5=2x-2+19
3x+3=2x+17
3x=2x+14
x=14
\(x-36:18+2.x+5=19+2\left(x-1\right)\)
\(\Leftrightarrow x+2x+5-\frac{36}{18}=19+2\left(x-1\right)\)
\(\Leftrightarrow3x+5-\frac{38}{16}=19+2\left(x-1\right)\)
\(\Leftrightarrow3x+5-2=19+2\left(x-1\right)\)
\(\Leftrightarrow3x+3=19+2\left(x-1\right)\)
\(\Leftrightarrow3x+3=2x+17\)
\(\Leftrightarrow3x=2x+17-3\)
\(\Leftrightarrow3x=2x+14\)
\(\Leftrightarrow3x=2x+14-2x\)
\(\Leftrightarrow x=14\)
=> x = 14
\(a,96-3\left(x+8\right)=42\\ \Rightarrow3\left(x+8\right)=54\\ \Rightarrow x+8=18\\ \Rightarrow x=10.\\ b,15.5\left(x-25\right)-225=0\\ \Rightarrow75\left(x-25\right)-225=0\\ \Rightarrow75\left(x-25\right)=225\\ \Rightarrow x-25=3\\ \Rightarrow x=28.\\ c,250:x+15=25\\ \Rightarrow250:x=10\\ \Rightarrow x=25\\ d,36:\left(x-5\right)=2^2\\ \Rightarrow36:\left(x-5\right)=4\\ \Rightarrow x-5=9\\ \Rightarrow x=14.\\ e,\left[3.\left(70-x\right)+5\right]:2=46\\ \Rightarrow3.\left(70-x\right)+5=92\\ \Rightarrow3\left(70-x\right)=87\\ \Rightarrow70-x=29\\ \Rightarrow x=41.\)
a: =>x(5-2)=120
=>3x=120
=>x=40
b: =>x(13-10)=240
=>3x=240
=>x=80
c; =>10x=250
=>x=25
d: =>3x=36
=>x=12
a, \(\frac{2}{x}=\frac{y}{4}\Leftrightarrow xy=8\)
Suy ra : \(x;y\inƯ\left(8\right)=\left\{1;2;4;8\right\}\)tự lập bảng
b, Xét : \(\frac{1}{x}=\frac{5}{15}\Leftrightarrow\frac{5}{5x}=\frac{5}{15}\Leftrightarrow x=3\)
\(\frac{y}{21}=\frac{5}{15}\Leftrightarrow15y=105\Leftrightarrow y=3\)
\(\frac{10}{z}=\frac{5}{15}\Leftrightarrow5z=150\Leftrightarrow z=30\)
c, tương tự b
dai the giai bao gio xong chac mua quyt nam sau moi giai xong
\(x^2-\left(-\frac{5}{36}\right)=\frac{14}{36}\)
\(x^2+\frac{5}{36}=\frac{14}{36}\)
\(x^2=\frac{14}{36}-\frac{5}{36}\)
\(x^2=\frac{1}{4}\)
\(\Rightarrow x\in\left\{\frac{-1}{2};\frac{1}{2};\frac{1}{-2};\frac{-1}{-2}\right\}\)
Vậy \(x\in\left\{\frac{-1}{2};\frac{1}{2};\frac{1}{-2};\frac{-1}{-2}\right\}\)
\(x^2-\left(\frac{-5}{36}\right)=\frac{14}{36}\Rightarrow x^2=\frac{14}{36}+\left(\frac{-5}{36}\right)=\frac{14}{36}-\frac{5}{36}=\frac{9}{36}=\frac{1}{4}\)
\(\Rightarrow x^2=\frac{1}{4}\Rightarrow x^2=\pm\left(\frac{1}{2}\right)^2\)
vậy x = \(\frac{1}{2}\) hoặc x = \(\frac{-1}{2}\)