b1 tính
a, 34-2:(3/5-1/2)
K
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8 tháng 7 2021
1) PT \(\Leftrightarrow\dfrac{x+3}{15}=\dfrac{4}{15}\) \(\Rightarrow x+3=4\) \(\Rightarrow x=1\)
Vậy ...
2) Mạnh dạn đoán đề là \(\left(2x-5\right)\left(x-3\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}2x-5=0\\x-3=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=3\end{matrix}\right.\)
Vậy ...
3) PT \(\Rightarrow3x-4-2x+5=3\)
\(\Rightarrow x=2\)
Vậy ...
4) PT \(\Rightarrow\left[{}\begin{matrix}2x+1=0\\\dfrac{1}{2}x-1=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=2\end{matrix}\right.\)
Vậy ...
8 tháng 7 2021
3) Ta có: \(\left(3x-4\right)-\left(2x-5\right)=3\)
\(\Leftrightarrow3x-4-2x+5=3\)
\(\Leftrightarrow x+1=3\)
hay x=2
HN
2
T
17 tháng 8 2023
\(a,\dfrac{2}{7}+\dfrac{5}{7}.\dfrac{7}{10}-\dfrac{1}{14}\)
\(=\dfrac{1}{7}.2+\dfrac{1}{7}.5.\dfrac{7}{10}-\dfrac{1}{7}.\dfrac{1}{2}\)
\(=\dfrac{1}{7}.\left(2+\dfrac{35}{10}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.\left(\dfrac{4}{2}+\dfrac{7}{2}-\dfrac{1}{2}\right)\)
\(=\dfrac{1}{7}.5=\dfrac{5}{7}\)
\(b,\left(3\dfrac{1}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\left(\dfrac{7}{2}-\dfrac{2}{3}\right).\dfrac{7}{34}-\dfrac{7}{34}.\dfrac{5}{7}\)
\(=\dfrac{7}{34}.\left(\dfrac{17}{6}-\dfrac{5}{7}\right)\)
\(=\dfrac{7}{34}.\dfrac{89}{42}=\dfrac{89}{204}\)
17 tháng 8 2023
a: =2/7-1/14+5/10
=2/7-1/14+1/2
=4/14-1/14+7/14
=10/14=5/7
b: =(7/2-2/3)*7/34-5/34
\(=\dfrac{21-4}{6}\cdot\dfrac{7}{34}-\dfrac{5}{34}\)
\(=\dfrac{7}{6}\cdot\dfrac{1}{2}-\dfrac{5}{34}=\dfrac{7}{12}-\dfrac{5}{34}=\dfrac{89}{204}\)
2 tháng 7 2019
b 1 tính
a) 3/5x2/7:4/9
=6/35:4/9
=6/35x9/4
=27/70
; 2/11:1/3x3/2
=2/11x3/1x3/2
=6/11x3/2
=9/11
c) 5/2+1/3+1/4
=30/12+4/12+3/12
=34/12+3/12
=37/12
; 1/2+1/4:1/6
=1/2+1/4.6/1
=1/2+3/2
=4/2
=2
chúc b học tốt
16 tháng 8 2021
a, \(3\left(2x+1\right)^2-2\left(x-5\right)^2+\left(x-1\right)\left(x+2\right)\)
\(=3\left(4x^2+4x+1\right)-2\left(x^2-10x+25\right)+x^2+x-2\)
\(=12x^2+12x+3-2x^2+20x-50+x^2+x-2\)
\(=11x^2+33x-49\)
16 tháng 8 2021
\(3\left(2x+1\right)^2-2\left(x-5\right)^2+\left(x-1\right)\left(x+2\right)\)
\(=3\left(4x^2+4x+1\right)-2\left(x^2-10x+10\right)+x^2+2x-x-2\)
\(=12x^2+12x+3-2x^2-20x-20+x^2+2x-x-2\)
\(=11x^2+33x-15\)
KT
6
9 tháng 1 2016
1/ 5(-2-1)-3(2-5)
=5.1-3.(-3)
=5-(-9)
=14
2/ 15(2-1)-3(4+2)
=15.1-3.8
=15-24
=-9
3/ -3(7-2)+5(4-3)
=-3.5+5.1
=-15+5
=-10
11 tháng 8 2023
2:
a: =4+3/8+5+2/3
=9+3/8+2/3
=216/24+9/24+16/24
=216/24+25/24
=241/24
b; =2+3/8+1+1/4+3+6/7
=6+3/8+1/4+6/7
=6+5/8+6/7
=419/56
c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)
=6+3/8-1/4+1/3
=6+1/8+1/3
=6+11/24
=155/24
d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)
=3+13+5/6
=16+5/6
=101/6
e: =3+1/2+4+5/7-5-5/14
=3+4-5+1/2+5/7-5/14
=2+7/14+10/14-5/14
=2+12/14
=2+6/7=20/7
f: =9/2+1/2:11/2
=9/2+1/11
=99/22+2/22=101/22
34 - 2 : (3/5 - 1/2)
= 34 - 2 : 1/10
= 34 - 20
= 14
Bài làm
\(34-2:\left(\frac{3}{5}-\frac{1}{2}\right)\)
\(=34-2:\left(\frac{6}{10}-\frac{5}{10}\right)\)
\(=34-2:\frac{1}{10}\)
\(=34-2x10\)
\(=34-20\)
\(=14\)
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