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a) x= 1/4
b) x= -7/144
c) x= 25/6
d) x=17/7
e) x= 80/63
f) x= -45/14
Câu a:
4/9.x = 1/9
x = 1/9 : 4/9
x = 1/9 x 9/4
x = 1/4
vậy x = 1/4
Câu b:
x : -1/2 = 7/12
x = 7/12 x (-1/2)
x = - 7/24
Vậy x = - 7/24
Câu c:
-5/4 : x = -3/10
x = -5/4 : (-3/10)
x = -5/4 x (-10/3)
x = 25/6
Vậy x = 25/6
\(a.\)
\(\frac{4}{9}.x=\frac{1}{9}\)
\(\Rightarrow x=\frac{1}{9}:\frac{4}{9}\)
\(\Rightarrow x=\frac{1}{9}.\frac{9}{4}\)
\(\Rightarrow x=\frac{1}{4}\)
Vậy \(x=\frac{1}{4}\)
\(b.\)
\(\frac{7}{18}.x-\frac{2}{3}=\frac{5}{18}\)
\(\Rightarrow\frac{7}{18}.x=\frac{5}{18}+\frac{2}{3}\)
\(\Rightarrow\frac{7}{18}.x=\frac{5}{18}+\frac{12}{18}\)
\(\Rightarrow\frac{7}{18}.x=\frac{17}{18}\)
\(\Rightarrow x=\frac{17}{18}:\frac{7}{18}\)
\(\Rightarrow x=\frac{17}{18}.\frac{18}{7}\)
\(\Rightarrow x=\frac{17}{7}\)
Vậy \(x=\frac{17}{7}\)
\(c.\)
\(x:-\frac{1}{12}=\frac{7}{12}\)
\(\Rightarrow x=\frac{7}{12}.-\frac{1}{12}\)
\(\Rightarrow x=-\frac{7}{144}\)
Vậy \(x=-\frac{7}{144}\)
\(d.\)
\(\frac{4}{9}-\frac{7}{8}.x=-\frac{2}{3}\)
\(\Rightarrow\frac{7}{8}.x=\frac{4}{9}-\left(-\frac{2}{3}\right)\)
\(\Rightarrow\frac{7}{8}.x=\frac{4}{9}+\frac{2}{3}\)
\(\Rightarrow\frac{7}{8}.x=\frac{4}{9}+\frac{6}{9}\)
\(\Rightarrow\frac{7}{8}.x=\frac{10}{9}\)
\(\Rightarrow x=\frac{10}{9}:\frac{7}{8}\)
\(\Rightarrow x=\frac{10}{9}.\frac{8}{7}\)
\(\Rightarrow x=\frac{80}{63}\)
Vây \(x=\frac{80}{63}\)
\(e.\)
\(-\frac{5}{14}:x=-\frac{3}{10}\)
\(\Rightarrow x=-\frac{5}{14}:-\frac{3}{10}\)
\(\Rightarrow x=-\frac{5}{14}.-\frac{10}{3}\)
\(\Rightarrow x=\frac{5}{7}.\frac{5}{3}\)
\(\Rightarrow x=\frac{25}{21}\)
Vậy \(x=\frac{25}{21}\)
\(g.\)
\(\frac{1}{6}+\frac{-5}{7}:x=-\frac{7}{18}\)
\(\Rightarrow-\frac{5}{7}:x=-\frac{7}{18}-\frac{1}{6}\)
\(\Rightarrow-\frac{5}{7}:x=-\frac{7}{18}-\frac{3}{18}\)
\(\Rightarrow-\frac{5}{7}:x=-\frac{10}{18}\)
\(\Rightarrow-\frac{5}{7}:x=-\frac{5}{9}\)
\(\Rightarrow x=-\frac{5}{7}:-\frac{5}{9}\)
\(\Rightarrow x=-\frac{5}{7}.-\frac{9}{5}\)
\(\Rightarrow x=\frac{9}{7}\)
Vậy \(x=\frac{9}{7}\)
a)15/8+3/4-5/12
=45+18-10/24
=53/24
b)11/24.12/33+5/6
=11.12/12.2.11.3+5/6
=1/6+5/6
=6/6=1
c)15/8+7/24:5/8
=15/8+7/24.8/5
=15/8+7.8/3.8.5
=15/8+7/15
=đề sai, nếu đúng thì như này
=8/15+7/15
=15/15=1
Câu 1:
16 - 18|x| = - 8 - 14|x|
18|x| - 14|x| = 16 + 8
4|x| = 24
|x| = 24 : 4
|x| = 6
x = - 6 hoăc x = 6
Vậy x ∈ {-6; 6}
e) 15-3|4x +2| = 3
3|4x + 2| = 15 - 3
3|4x + 2| = 12
|4x + 2| = 12 : 3
|4x + 2| = 4
4x + 2 = -4 hoặc 4x + 2 = 4
Th1: 4x + 2 = - 4
4x = - 4 - 2
4x = - 6
x = - 6/4
x = - 3/2
Th2: 4x + 2 = 4
4x = 4 - 2
4x = 2
x = 2/4
x = 1/2
Vậy x ∈ {- 3/2; 1/2}
Câu 1:
16 - 18|x| = - 8 - 14|x|
18|x| - 14|x| = 16 + 8
4|x| = 24
|x| = 24 : 4
|x| = 6
x = - 6 hoăc x = 6
Vậy x ∈ {-6; 6}
A=1+2+3+...+70
A=(70+1).[(70-1):1+1]:2
A=71.70:2
A=4970:2
A=2485
B=5+10+15+...+100
B=(100+5).[(100-5):5+1]:2
B=105.20:2
B=2100:2
B=1050