Tìmx
a)2/3+x=5/7+7/17:49/34 b)x-4/5+5/9=28/45
c)x:6/7+2/3=7/3 d)15/21:x=3/7+2008/2009*2000/2008+9/2008*2008/2009
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\(\frac{15}{21}:x=\frac{3}{7}+\frac{2008}{2009}.\frac{2000}{2008}+\frac{9}{2008}.\frac{2008}{2009}\)
\(\frac{15}{21}:x=\frac{3}{7}+\frac{2000}{2009}+\frac{9}{2009}=\frac{3}{7}+\frac{2009}{2009}=\frac{10}{7}\)
\(x=\frac{15}{21}:\frac{10}{7}=\frac{15}{21}.\frac{7}{10}=\frac{1}{2}\)
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{8}\right):15\frac{3}{2}=2008\)
\(\Leftrightarrow2009-\left(\frac{41}{9}+x-\frac{63}{8}\right):\frac{33}{2}=2008\)
\(\Leftrightarrow2009-\left(x-\frac{239}{72}\right):\frac{33}{2}=2008\)
\(\Leftrightarrow2009-\frac{2x}{33}+\frac{239}{1188}=2008\)
\(\Leftrightarrow\frac{-2x}{33}=\frac{-1427}{1188}\)
\(\Leftrightarrow-2376x=-47091\)
\(\Leftrightarrow x=\frac{1427}{72}\)
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
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{18}\right):15\frac{2}{3}=2008\)
\(2009-\left(\frac{41}{9}+x-\frac{133}{18}\right):\frac{47}{3}=2008\)
\(\left(\frac{41}{9}+x-\frac{133}{18}\right):\frac{47}{3}=2009-2008\)
\(\left(\frac{41}{9}+x-\frac{133}{18}\right):\frac{47}{3}=1\)
\(\frac{41}{9}+x-\frac{133}{18}=1\cdot\frac{47}{3}\)
\(\frac{41}{9}+x-\frac{133}{18}=\frac{47}{3}\)
\(\frac{41}{9}+x=\frac{133}{18}+\frac{47}{3}\)
\(\frac{41}{9}+x=\frac{415}{18}\)
\(x=\frac{415}{18}-\frac{41}{9}\)
\(x=\frac{37}{2}\)
\(2009-\left(4\frac{5}{9}+x-7\frac{7}{18}\right)\div15\frac{2}{3}=2008\)
\(\left(4\frac{5}{9}+x-7\frac{7}{18}\right)\div15\frac{2}{3}=2009-2008\)
\(\left(-3\frac{3}{18}+x\right)\div15\frac{2}{3}=1\)
\(-3\frac{3}{18}+x=15\frac{2}{3}\)
\(x=15\frac{2}{3}+3\frac{3}{18}\)
\(x=15\frac{12}{18}+3\frac{3}{18}\)
\(x=18\frac{15}{18}\)
exactly 100%
Tìm x:
\(a.\frac{2}{3}+x=\frac{5}{7}+\frac{7}{17}\div\frac{49}{34}\)
\(\frac{2}{3}+x=1\)
\(x=1-\frac{2}{3}\)
\(x=\frac{1}{3}.\)
\(b.x-\frac{4}{6}+\frac{5}{9}=\frac{28}{45}\)
\(x-\frac{4}{6}=\frac{28}{45}-\frac{5}{9}\)
\(x-\frac{4}{6}=\frac{1}{15}\)
\(x=\frac{1}{15}+\frac{4}{6}\)
\(x=\frac{11}{15}.\)
\(c.x\div\frac{6}{7}+\frac{2}{3}=\frac{7}{3}\)
\(x\div\frac{6}{7}=\frac{7}{3}-\frac{2}{3}\)
\(x\div\frac{6}{7}=\frac{5}{3}\)
\(x=\frac{5}{3}\times\frac{6}{7}\)
\(x=\frac{30}{21}.\)
\(d.\frac{15}{21}\div x=\frac{3}{7}+\frac{2008}{2009}\times\frac{2000}{2008}+\frac{9}{2008}\times\frac{2008}{2009}\)
\(\frac{5}{7}\div x=\frac{10}{7}\)
\(x=\frac{10}{7}\times\frac{5}{7}\)
\(x=\frac{50}{49}.\)