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\(=13\left(55+85\right)+87\left(51+69\right)\)
\(=13\cdot140+87\cdot120\)
\(=12260\)
a: \(=100\cdot104=10400\)
d: \(=2\cdot9+4\cdot27=18+108=126\)
c: \(=520:\left\{\left[\left(80+20\right):2-2\right]+82\right\}+1\)
\(=520:130+1\)
=4+1
=5
c, 50 - 1 . ( -40 - 10 )
= 50 - 1 . -50
= 50 + 50
= 100
a, 25 - 34 - 25 + (-45) + 34
= ( 25 - 25 ) - (-34 + 34) + -45
= -45
c: \(=520:\left\{\left[\left(80+20\right):2-2\right]+82\right\}+1\)
\(=520:\left\{48+82\right\}+1\)
=4+1
=5
Bài 1:
a) Ta có: \(x\left(x^2-4\right)=0\)
\(\Leftrightarrow x\left(x-2\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)
Vậy: \(x\in\left\{0;2;-2\right\}\)
b) Ta có: \(\left(2x-3\right)+\left(-3x\right)-\left(x-5\right)=40\)
\(\Leftrightarrow2x-3-3x-x+5=40\)
\(\Leftrightarrow-2x+2=40\)
\(\Leftrightarrow-2x=38\)
hay x=-19
Vậy: x=-19
Bài 2:
a) Ta có: \(-45\cdot12+34\cdot\left(-45\right)-45\cdot54\)
\(=-45\cdot\left(12+34+54\right)\)
\(=-45\cdot100\)
\(=-4500\)
b) Ta có: \(43\cdot\left(57-33\right)+33\cdot\left(43-57\right)\)
\(=43\cdot57-43\cdot33+43\cdot33-33\cdot57\)
\(=43\cdot57-33\cdot57\)
\(=57\cdot\left(43-33\right)\)
\(=57\cdot10=570\)
a, 19.64 + 76.34
= 19.64 + 19.4.34
= 19.64 + 19.136
= 19.(64 + 136)
= 19.200
= 3800
b, 35.12 + 65.13
= 35.12 + 65.12 + 65
= 12.(35+65) + 65
= 12.100 + 65
= 1200 + 65
= 1265
a, 19.64 + 76.34
= 19.64 + 19.4.34
= 19.64 + 19.136
= 19.(64 + 136)
= 19.200
= 3800
b, 35.12 + 65.13
= 35.12 + 65.(12 + 1)
= 35.12 + 65.12 + 65
= 12.(35 + 65) + 65
= 12.100 + 65
= 1200 + 65
= 1265
c, 136.68 + 16.272
= 136.68 + 16.2.136
= 136.68 + 32.136
= 136.(68 + 32)
= 136.100
= 13600
d, 19991999.1998 - 19981998.1999
= 1999.10001.1998 - 19981998.1999
= 1999.19981998-19981998.1999
= 0
Chúc bạn học tốt !!!!!!!
`19.64 + 19.37 - 19`
`= 19.64 + 19.37 - 19.1`
`= 19.(64 + 37 - 1)`
`= 19 . 100`
`= 1900`
`45.12 + 13.55`
`= 45 . 12 + (1+12).55`
`= 45 . 12 + 55 + 12.55`
`= 12 . (45 + 55) + 55`
`= 12 . 100 + 55`
`=1200 + 55`
`=1255`
a: \(19\cdot64+19\cdot37-19\)
\(=19\left(64+37-1\right)\)
\(=19\cdot100=1900\)
b: \(45\cdot12+13\cdot55\)
\(=540+715\)
=1255