3-4/5:1/3; 5/9x2/7-3/7;12/8-3/4+3
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19 tháng 3 2016
1+2+3+4+5+6+7+8+9x2:5 = 1+2+3+4+5+6+7+8+18:5=1+2+3+4+5+6+7+8+3.6=39.6
24 tháng 4 2021
a) \(1678\cdot24+77\cdot1678-1678=1678\left(24+77-1\right)=167800\)
24 tháng 4 2021
b) Ta có: \(\dfrac{2}{5}+\dfrac{4}{11}+\dfrac{3}{5}+\dfrac{18}{11}+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{4}{11}+\dfrac{18}{11}\right)+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=3+\dfrac{1}{4}+\dfrac{1}{6}\)
\(=\dfrac{36}{12}+\dfrac{3}{12}+\dfrac{2}{12}=\dfrac{41}{12}\)
HP
21 tháng 9 2021
a. 9x2 - 6x - 3 = 0
<=> 3(3x2 - 2x - 1) = 0
<=> 3(3x2 - 3x + x - 1) = 0
<=> \(3\left[3x\left(x-1\right)+\left(x-1\right)\right]=0\)
<=> 3(3x + 1)(x - 1) = 0
<=> \(\left[{}\begin{matrix}3x+1=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{3}\\x=1\end{matrix}\right.\)
b. (2x + 1)2 - 4(x + 2)2 = 9
<=> (2x + 1)2 - \(\left[2\left(x+2\right)\right]^2=9\)
<=> (2x + 1 - 2x - 4)(2x + 1 + 2x + 4) = 9
<=> -3(4x + 5) = 9
<=> 4x + 5 = -3
<=> 5 + 3 = -4x
<=> -4x = 8
<=> -x = 2
<=> x = -2
21 tháng 9 2021
a) \(\Leftrightarrow\left(9x^2-6x+1\right)-4=0\)
\(\Leftrightarrow\left(3x-1\right)^2-4=0\)
\(\Leftrightarrow3\left(x-1\right)\left(3x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)
b) \(\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\)
\(\Leftrightarrow12x=-24\Leftrightarrow x=-2\)
c) \(\Leftrightarrow3x^2-6x+3-3x^2+15x=21\)
\(\Leftrightarrow9x=18\Leftrightarrow x=2\)
d) \(\Leftrightarrow x^2+6x+9-x^2-4x+32=1\)
\(\Leftrightarrow2x=-40\Leftrightarrow x=-20\)
`3-4/5:1/3`
`=3-4/5xx3/1`
`=3-12/5`
`=15/5-12/5`
`=3/5`
`5/9xx2/7-3/7`
`=10/63-3/7`
`=10/63-27/63`
`=-17/63`
`12/8-3/4+3`
`=12/8-6/8+24/8`
`=30/8=15/4`
3−4/5:1/3
=3−4/5��3/1=3−4/5xx3/1
=3−12/5=3−12/5
=15/5−12/5=15/5−12/5
=3/5=3/5
5/9��2/7−3/75/9xx2/7−3/7
=10/63−3/7=10/63−3/7
=10/63−27/63=10/63−27/63
=−17/63=−17/63
12/8−3/4+312/8−3/4+3
=12/8−6/8+24/8=12/8−6/8+24/8
=30/8=15/4=30/8=15/4