( -2/5)^2 +1/2.(4,5-2) - 25%
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a] 425 . 7 . 4 - 170 . 60
= ( 425 . 4 ) - ( 7 .170 ) . 60
= 1700 - 1190 . 60
= 510 . 60
= 30600
a] 425 . 7 .4 - 170 . 60
= ( 425 . 4 ) . 7 - ( 170 . 10 ) . 6
= 1700 . 7 - 1700 . 6
= 1700 . ( 7-6 )
= 1700 . 1
= 1700
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a] 17 . 82 + 19 . 17 - 17
= 17 . 82 + 19 . 17 - 17.1
= 17 . ( 82 + 19 - 1 )
= 17 . 100
= 1 700
a] 17 . 82 + 19 . 17 - 17
= 17 . ( 82 + 19 - 17 )
= 17 . 84
= 1428
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a, \(A=\left(2011-1\right)\left(2011+1\right)=2011^2-1< B\)
b, \(C=\left(2012-2\right)\left(2012+2\right)=2012^2-4< D\)
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a] 28 . 62 - 28 . 57
= 28 . ( 62 - 57 )
= 28 . 5
= 140
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a, \(\left(x+1\right)\left(x+2\right)=1.12=2.6=3.4\)
TH1 \(\left\{{}\begin{matrix}x+1=1\\x+2=12\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0\\x=10\end{matrix}\right.\)
TH2 \(\left\{{}\begin{matrix}x+1=2\\x+2=6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\x=4\end{matrix}\right.\)
TH3 : \(\left\{{}\begin{matrix}x+1=3\\x+2=4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\x=2\end{matrix}\right.\)
b, \(x^2+x-12=0\Leftrightarrow\left(x+4\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=3\end{matrix}\right.\)
c, \(\dfrac{x+5}{x}=1+\dfrac{5}{x}\Rightarrow x\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)
x+5 | 1 | -1 | 5 | -5 |
x | -4 | -6 | 0 | -10 |
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3, tính :
a) 1/1.2 + 1/3.4 + ... + 1/98.99 + 1/99.100
= \(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+....+\dfrac{1}{98}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\)
= \(1-\dfrac{1}{100}\)
= \(\dfrac{99}{100}\)
b, 3/1.4 + 3/4.7 + ... + 3/88.91 + 3/91.94
= \(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{88}-\dfrac{1}{91}+\dfrac{1}{91}-\dfrac{1}{94}\)
= \(1-\dfrac{1}{94}\)
= \(\)\(\dfrac{93}{94}\)
c, 1/5 + 1/50 + 1/150 + 1/300 + 1/500
= 300/1500 + 30/1500 + 10/1500 + 5/1500 +3/1500
= 29/125
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2 . 14 . 47 + 7 . 53 . 4
= 2 .2.7 . 47 + 7 . 53 . 2.2
= 2.2.7 . ( 47 + 53 )
= 2.2.7 . 100
= 4.7.100
= 28.100
= 2800
2 . 14 . 47 + 7 . 53 . 4
= 2 .2.7 . 47 + 7 . 53 . 2.2
= 2.2.7 . ( 47 + 53 )
= 2.2.7 . 100
= 4.7.100
= 28.100
= 2800
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( 25/14 + 3 . 13/42 ) : 3/7
= ( 25/14 + 13/14 ) : 3/7
= 19/7 : 3/7
= 19/3
7/9 + 5/9 . 11/23 + 5/9 .12 / 23
= 7/9 + 5/9 . ( 11/23 + 12/23 )
= 7/9 + 5/9 . 1
= 7/9 + 5/9
= 4/3
=(25/14 + 13/14) : 3/7 = 3/7 : 19/7 = 3/19
= 7/9 + 5/9( 11/23+12/23) =7/9 +5/9.1 =7/9+5/9=4/3
đây nhá
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Nhưng em nhìn phát là biết vế trước bé hơn về sau rồi anh a
\(=\dfrac{4}{25}+\dfrac{1}{2}\left(\dfrac{9}{2}-2\right)-\dfrac{1}{4}=\dfrac{4}{25}+\dfrac{1}{2}\left(\dfrac{5}{2}\right)-\dfrac{1}{4}=\dfrac{4}{25}+\dfrac{5}{4}-\dfrac{1}{4}=\dfrac{4}{25}+1=\dfrac{29}{25}\)
`(-2/5)^2 + 1/2 . (4,5 - 2) - 25%`
`=4/25 + 1/2 . (9/2 - 2) - 1/4`
`=4/25 + 1/2 . (9/2 - 4/2)-1/4`
`=4/25 + 1/2 . 5/2 - 1/4`
`=4/25 + 5/4 - 1/4`
`=4/25 + 1`
`=4/25 + 25/25`
`=29/25`