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\(a,\Rightarrow x\times\left(42+54+4\right)=25400\\ \Rightarrow x\times100=25400\\ \Rightarrow x=254\\ b,\Rightarrow x\times\left(142-41-1\right)=40800\\ \Rightarrow x\times100=40800\\ \Rightarrow x=408\)
a) \(x\)(42+54+4)=15400 b) (142-41-1)\(x\)=10800
\(x\)x100=15400 100x\(x\)=10800
\(x\)=15400:100 \(x\)=10800:100
\(x\)=154 \(x\)=108
Xx42+Xx57+X=25400
Xx(42+57+1)=25400
Xx100=25400
X=25400:100
X=254
\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}\)
= \(\frac{7}{7}-\frac{1}{7}\)
= \(\frac{6}{7}\)
2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)
\(x.\frac{4}{3}=\frac{113}{76}\)
\(x=\frac{113}{76}:\frac{4}{3}\)
\(x=\frac{399}{304}\)
VẬY \(x=\frac{399}{304}\)
b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
Vậy \(x=\frac{29}{36}\)
c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)
\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)
\(x.2=\frac{4}{5}\)
\(x=\frac{4}{5}:2\)
\(x=\frac{2}{5}\)
Vậy \(x=\frac{2}{5}\)
Chúc bạn học tốt !!!
Y x 42 +Yx 57 + Y = 25400
=> Y x (42 + 57 + 1) = 25400
=> Y x 100 = 25400
=> Y = 25400 : 100
=> Y = 254
Y x 42 +Yx 57 + Y = 25400
Y x ( 42 + 57 ) + Y = 25400
Y x 99 + Y = 25400
a) y x 42 + y x 57 + y = 25 400
y x ( 42 + 57 + 1 ) = 25 400
y x 100 = 25 400
y = 25 400 : 100
y = 254
b) 142 x y - 41 x y - y = 408 000
y x ( 142 - 41 - 1 ) = 408 000
y x 100 = 408 000
y = 408 000 : 100
y = 4 080
a.y*(42+57+1)=25400
y*100=25400
y=25400:100=254
b.(142-41-1)*y=408000
100*y=408000
y=408000:100=4080
c, ( 3996 - x ) : 36 = 54
(3996 - x ) = 54 × 36
(3996 - x ) = 1944
x = 3996 - 1944
x - 2052
d, x × 42 + x × 4 = 25400
x × ( 42 + 4 ) =25400
x × 46 = 25400
x = 25400 : 46
x = ...