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a,\(\left(\dfrac{-2}{3}+\dfrac{3}{7}\right):\dfrac{4}{5}+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right):\dfrac{4}{5}\)
\(=\left(-\dfrac{2}{3}+\dfrac{3}{7}\right).\dfrac{5}{4}+\left(\dfrac{-1}{3}+\dfrac{4}{7}\right).\dfrac{5}{4}\)
\(=\left(\dfrac{-2}{3}+\dfrac{3}{7}+\dfrac{-1}{3}+\dfrac{4}{7}\right).\dfrac{5}{4}\)
\(=\left(-1+1\right).\dfrac{5}{4}=0\)
Chúc bạn học tốt!!!
Câu b làm tương tự!
a) Đoàn Đức Hiếu
b) \(\dfrac{5}{9}:\left(\dfrac{1}{11}-\dfrac{5}{22}\right)+\dfrac{5}{9}:\left(\dfrac{1}{15}-\dfrac{2}{3}\right)\)
\(=\dfrac{5}{9}:\left(-\dfrac{3}{22}\right)+\dfrac{5}{9}:\left(-\dfrac{3}{5}\right)\)
\(=-\dfrac{5}{9}\cdot\dfrac{22}{3}-\dfrac{5}{9}\cdot\dfrac{5}{3}\)
\(=-\dfrac{110}{27}-\dfrac{25}{27}\)
\(=-5\)
\(a,\frac{8^{12}.5^{21}}{2^{17}.10^{19}}=\frac{\left(2^3\right)^{12}.5^{21}}{2^{17}.2^{19}.5^{19}}=\frac{2^{36}.5^{21}}{2^{36}.5^{19}}=25\)
\(b,\left(x-5\right).\left(x+\frac{1}{2}\right)=0\)
\(\Rightarrow x-5=0\)hoặc \(x+\frac{1}{2}=0\)
\(x=5\)hoặc \(x=-\frac{1}{2}\)
\(c,\left|x-6\right|-\frac{1}{2}=\frac{3}{2}\)
\(\left|x-6\right|=2\)
\(\Rightarrow x-6=2\)hoặc \(x-6=-2\)
\(x=8\)hoặc \(x=4\)
1,
\(\frac{25}{12}+\left(\frac{-4}{12}\right)=\frac{7}{4}\)
\(\frac{-10}{8}+\frac{15}{4}=\frac{5}{2}\)
\(\frac{3}{8}+\frac{-14}{6}=\frac{-47}{24}\)
\(\frac{350}{150}+\left(\frac{-200}{360}\right)=\frac{16}{9}\)
\([\frac{5}{8}+\left(\frac{-3}{4}\right)]+\frac{15}{6}=\frac{-1}{8}+\frac{15}{6}=\frac{19}{8}\)
\(\frac{7}{3}+[\left(\frac{-5}{6}\right)+\left(\frac{-2}{3}\right)]=\frac{7}{3}+\left(\frac{-3}{2}\right)=\frac{5}{6}\)
4,
\(\frac{X+1}{5}=\frac{3}{7}\)
\(\Rightarrow\left(X-1\right).7=3.5\)
\(\Rightarrow7X-7=15\)
\(\Rightarrow7X=22\)
\(\Rightarrow X=\frac{22}{7}\)
\(\frac{X-3}{4}=\frac{1}{2}\)
\(\Rightarrow\left(X-3\right)2=1.4\)
\(\Rightarrow2X-6=4\)
\(\Rightarrow2X=10\)
\(\Rightarrow X=5\)
Tôi ko bt
1. Tính các tổng sau
25/12+-4/12 = 25/12-4/12 = 21/12 = 7/4
-10/8+15/4 = -10/8+30/8 = 20/8 = 5/2
3/8+-14/6 = 3/8-7/3 = 9/24-56/24 = -47/24
350/150+-200/360 = 7/3-5/9 = 21/9-5/9 = 16/9
[5/8+(-3/4)]+15/6 = [5/8-6/8]+5/2 = -1/8+5/2 = -1/8+20/8 = 19/8
7/3+[(-5/6)+(-2/3)] = 7/3+[-5/6-4/6] = 7/3+[-9/6] = 7/3-9/6 = 14/6-9/6 = 5/6
2. Tính nhanh:
(5/-7+-5/-7)+4/3 = (-5/7+5/7)+4/3 = 0+4/3 = 4/3
10/3+(10/-3+2) = 10/3-10/3+2 = 0+2 = 2
(-15/12+ 3/-4)+15/12 = -15/12-3/4+15/12 = (-15/12+15/12)-3/4 = 0-3/4= -3/4
3. Tính:
1/3/5+5/6 = 5/3+5/6 = 10/5+5/6 = 15/6 = 5/2
3/3/7+2/1/2 = 7+4 = 11
3/1/4-1/1/3 = 12-3 = 9
2/3/5-1/1/5 = 10/3-5 = 10/3-15/3 = -5/3
5454/5757-171717/191919 = 54/57-17/19 =18/19-17/19 = 1/19
2/5--3/11 = 2/5+3/11 = 22/55+15/55 = 37/55
-34/37x74/-85 = -2516/-3145 = 4/5
-5/9:-17/18 = -5/6x-18/17 = -5x-18/6/17 = 5x3x6/6x17 = 5x3/17 = 15/17
4. Tìm x biết:
X+1/5=3/7
X=3/7-1/5
X=8/35
Vậy X=8/35
X-3/4=1/2
X=1/2+3/4
X=5/4
Vậy X=5/4
11/12-(2/5+X)=2/3
2/5+X=11/12-2/3
2/5+X=1/4
X=1/4-2/5
X=-3/20
Vậy X=-3/20
2X(X-1/7)=0
=>2X=0 hoặc X-1/7=0
X=0:2 hoặc X=0+1/7
X=0 hoặc X=1/7
Vậy X thuộc {0;1/7}
3/4+1/4:X=2/5
1/4:X=2/5-3/4
1/4:X=-7/20
X= 1/4:-7/20
X=-5/7
Vậy X=-5/7
X+1/3=5/12
X=5/12-1/3
X=1/12
Vậy X=1/12
=)) ờm... gửi muộn ghê