178 x 23 = ?
846 x 83 = ?
340 x 47 = ?
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846 : [41 - (7x - 5)] = 47
41 - (7x - 5)=846:47=18
7x - 5=41-18=23
7x=23+5=28
x=28:7=4
a: \(x\in\varnothing\)
b: \(\Leftrightarrow\left[{}\begin{matrix}4x-1=15\\4x-1=-15\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-\dfrac{7}{2}\end{matrix}\right.\)
47 x 83 + 21 x 53 + 47 x 17 - 79 x 53
= 47 x (83 + 17) + 53 x (21 - 79)
= 47 x 100 + 53 x (-58)
= 4700 - 3074
= 1626
\(47.83+21.53+47.17-79.53\)
\(=47.\left(83+17\right)+53.\left(79+21\right)\)
\(=47.100+53.100\)
\(=4700+5300\)
\(=10000\)
Tính nhanh:
a, 18,25 - 3,78 + 1,58
= 18,25 - ( 3,78 + 1,58 )
= 18,25 - 5,36
= 12,89
b, 183 x ( 48 + 54 ) - 83 x ( 54 + 48 )
= 183 x 102 - 83 x 102
= 102 x ( 183 - 83 )
= 102 x 100
= 10200
c, 2,4 x 178 x 2 - 3 x 78 x 1,6
= ( 2,4 x 178 x 2 ) - ( 3 x 78 x 1,6 )
= ( 427,2 x 2 ) - ( 3 x 124,8 )
= 854,4 - 374,4
= 480
d, 3,9 x 138 - 7,8 x 19
= ( 3,9 x 138 ) - ( 7,8 x 19 )
= 538,2 - 148,2
= 390.
\(\dfrac{1}{2}\) xy=\(\dfrac{17}{42}\)
=\(\dfrac{17}{42}\):\(\dfrac{1}{2}\)
= \(\dfrac{34}{42}\)
\(23+\frac{x}{47-x}=\frac{2}{3}\)
\(\frac{x}{47-x}=\frac{-67}{3}\)\(\Rightarrow\orbr{\begin{cases}x=-67\\47-x=3\Rightarrow x=44\end{cases}}\)
\(23-\frac{x}{47+x}=\frac{1}{3}\)
\(\frac{x}{47+x}=\frac{68}{3}\)\(\Rightarrow\orbr{\begin{cases}x=68\\47+x=3\Rightarrow x=-44\end{cases}}\)
x-(57-(42+(-23-x)=13-47+25-23-x
x-57-42-23-x=13-47+25-23-x
x-122-x=-32-x
x-x-122=-32-x
-32-x=-122
x=-32-(-122)
x=90
Vậy x=90
\(x-(57-(42+(-23-x)=13-47+25-13-x\)
\(\Rightarrow x-57-42+\left(-23\right)-x=13-47+25-23-x\)
\(\Rightarrow x-x+x=13-47+25-23+23+42+57\)
\(\Rightarrow x=90\)
4094
70218
15980
TL:
178 x 23 = 4094
846 x 83 = 70218
340 x 47 = 15980
-HT-