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3/4 * x + 1/2 * x -15 = 35
3/4 * x +1/2 * x = 35 + 15
3/4 * x +1/2 * x = 50
x * ( 3/4 + 1/2 ) = 50
x * 5/4 = 50
x = 50 : 5/4
x = 40
phan b mik ko nhap dc nen bn tu lm nha
a, \(\frac{3}{4}\times x+\frac{1}{2}\times x-15=35\)
\(x+x-15=\frac{3}{4}-\frac{1}{2}\)
\(x+x-15=\frac{2}{8}=\frac{1}{4}\)
\(x=35-15\)
\(x=20\)
Vậy \(x=\frac{1}{4}\)và \(x=20\)
b, Chịu
\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+....+\frac{1}{x\left(x+2\right)}=\frac{8}{17}\)
\(\Leftrightarrow2\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+....+\frac{1}{x\left(x+2\right)}\right)=2.\frac{8}{17}\)
\(\Leftrightarrow\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+....+\frac{2}{x\left(x+2\right)}=\frac{16}{17}\)
\(\Leftrightarrow1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{x}-\frac{1}{x+2}=\frac{16}{17}\)
\(\Leftrightarrow1-\frac{1}{x+2}=\frac{16}{17}\)
\(\Leftrightarrow\frac{1}{x+2}=1-\frac{16}{17}=\frac{1}{17}\)
\(\Rightarrow x+2=17\Rightarrow x=15\)
Bài 1:
b) \(71+65.4=\frac{x+140}{x}+260\)
\(\Rightarrow331=\frac{x+140}{x}+260\)
\(\Rightarrow\frac{x+140}{x}=71\)
\(\Rightarrow x+140=71x\)
\(\Rightarrow71x-x=140\)
\(\Rightarrow70x=140\)
\(\Rightarrow x=2\)
Vậy ...
c) \(7:\left(\frac{3,8.x}{19}+3\right)=1,75\)
\(\frac{3,8.x}{19}+3=4\)
\(\frac{3,8.x}{19}=1\)
\(3,8.x=19\)
\(x=5\)
vaayj ...
x-4/5=5/2x4/15
x-4/5=2/3
x=2/3+4/5
x=8/15
(dấu / là dấu bằng giữa tử và mẫu)
\(x-\frac{4}{5}=\frac{5}{2}x\frac{4}{15}\)
\(x-\frac{4}{5}=\frac{2}{3}\)
\(x=\frac{2}{3}+\frac{4}{5}\)
\(x=\frac{22}{15}\)
nha bn
\(\frac{1}{2}\times x+\frac{2}{3}=\frac{5}{2}\)
\(\frac{1}{2}\times x=\frac{5}{2}-\frac{2}{3}\)
\(\frac{1}{2}\times x=\frac{11}{6}\)
\(x=\frac{11}{6}\div\frac{1}{2}\)
\(x=\frac{11}{3}\)
3/4x + 1/2x -15 = 35
(3/4 + 1/2) x X = 15 + 35 = 50
5/4 x X= 50
X = 50 : 5/4
X = 40
Câu b:
\(\frac{27,5\times8,4}{x}\times7=21\)
\(\frac{27,5\times8,4}{x}=3\)
\(\frac{231}{x}=3\)
x = 231 : 3
x = 77