Trong bài phép chia phân số (Chương trình VNEN)
Tìm x
a ) 4/9.x = 1/9
b) 7/18 . x - 2/3 = 5/18
c) x:-1/12 = 7/12
d) 4/9- 7/8.x = -2/3
e) -5/14 : x = -3/10
g) 1/6 + -5/7 : x = -7/18
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Ai tk mình mình tk lại nha !!!
a) x= 1/4
b) x= -7/144
c) x= 25/6
d) x=17/7
e) x= 80/63
f) x= -45/14
Tính nhanh mỗi biểu thức sau:
a, 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20
= (0 + 20) + (1 + 19) + (2 + 18) + (3 + 17) + (4 + 16) + (5 + 15) + (6 + 14) + (7 + 13) + (8 + 12) + (9 + 11) + 10
= 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 10
= 20 x 10 + 10
= 200 + 10
= 210
b, 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (4 x 9 - 36)
= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (36 - 36)
= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 0
= A x 0
= 0
c, (81 - 7 x 9 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)
= (81 - 63 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)
= (18 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)
= 0 :(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)
= 0 : A
= 0
d, (6 x 5 + 7 - 37) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= (30 + 7 - 37) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= (37 - 37) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= 0 x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= 0 x A
= 0
e, (11 x 9 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)
= (99 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)
= (99 + 1 - 100) : (1 x 2 x 3 x 4 x ... x 10)
= (100 - 100) : (1 x 2 x 3 x 4 x ... x 10)
= 0 : (1 x 2 x 3 x 4 x ... x 10)
= 0 : A
= 0
g, (m : 1 - m x 1) : (m x 2008 + m x 2008)
= (m - m) : (m x 2008 + m x 2008)
= 0 : (m x 2008 + m x 2008)
= 0 : A
= 0
h, (2 + 4 + 6 + 8 + m x n) x (324 x 3 - 972)
= (2 + 4 + 6 + 8 + m x n) x (972 - 972)
= (2 + 4 + 6 + 8 + m x n) x 0
= A x 0
= 0
l, (1 + 2 + 3 + ... + 99) x (13 x 15 - 12 x 15 - 15)
= (1 + 2 + 3 + ... + 99) x (15 x (13 - 12 - 1))
= (1 + 2 + 3 + ... + 99) x (15 x 0)
= (1 + 2 + 3 + ... + 99) x 0
= A x 0
= 0
i, (0 x 1 x 2 x...x 99 x 100) : (2 + 4 + 6 +...+ 98)
= 0 x : (2 + 4 + 6 +...+ 98)
= 0 x A
= 0
k, (0 + 1 + 2 +...+ 97 + 99) x (45 x 3 - 45 x 2 - 45)
= (0 + 1 + 2 +...+ 97 + 99) x (45 x (3 - 2 - 4))
= (0 + 1 + 2 +...+ 97 + 99) x (45 x 0)
= (0 + 1 + 2 +...+ 97 + 99) x 0
= A x 0
= 0
a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
Bài 1:
1; ( - 35) : (-7) = 5
2; (- 42) : 21 = - 2
3; 45 : (-9) = -5
4; 18 : 9 = 2
5; (- 30) : (- 15) = 2
6; 0 : 18 = 0
7; 0 : (-13) = 0
8; 44 : (-4) = - 11
9; - 55 : 11 = - 5
10; 46 : 23 = 2
\(a.\)
\(\frac{4}{9}.x=\frac{1}{9}\)
\(\Rightarrow x=\frac{1}{9}:\frac{4}{9}\)
\(\Rightarrow x=\frac{1}{9}.\frac{9}{4}\)
\(\Rightarrow x=\frac{1}{4}\)
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 \(x=\frac{9}{7}\)