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\(2^{x+1}=4=2^2\Rightarrow x+1=2\Rightarrow x=1\)
\(2^{x-1}=4=2^2\Rightarrow x-1=2\Rightarrow x=3\)
\(2^x.4=128=4.32=4.2^5\Rightarrow x=5\)
\(3^{x-2}.9=81=9.9=9.3^2\Rightarrow x-2=2\Rightarrow x=4\)
\(\frac{3^{x+1}}{9}=3\Rightarrow3^{x+1}=27=3^3\Rightarrow x=2\)
\(41-2^x=9\Rightarrow2^x=41-9=32=2^5\Rightarrow x=5\)
Quá 20h rồi không biết được ko
tớ cũng học bồi dưỡng ,,k minh nha
giải
ta có:B=1/1x2x3+1/2x3x4+... +1/18x19x220
=>2B=2/1x2x3+2/2x3x4+...2/18x19x20
=(1/1x2-1/2x3)+(1/2x3-1/3x4)+..+(1/18x19-1/19x20)
=1/1x2-1/19x20=189/380
=>B=189/760<1/4
kb đi có gì tớ giải cho
a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)
\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)
\(\Rightarrow x=\dfrac{-5}{12}\)
b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{2}{5}\)
c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)
\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-77}{120}\)
d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)
\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{-7}{20}\)
e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)
\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-59}{105}\)
g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-13}{12}\)
Giải:
a) \(2\dfrac{17}{20}-1\dfrac{15}{11}+6\dfrac{9}{20}:3\)
\(=\dfrac{57}{20}-\dfrac{26}{11}+\dfrac{129}{20}:3\)
\(=\dfrac{107}{220}+\dfrac{43}{20}\)
\(=\dfrac{29}{11}\)
b) \(4\dfrac{3}{7}:\left(\dfrac{7}{5}.4\dfrac{3}{7}\right)\)
\(=\dfrac{31}{7}:\left(\dfrac{7}{5}.\dfrac{31}{7}\right)\)
\(=\dfrac{31}{7}:\dfrac{31}{5}\)
\(=\dfrac{5}{7}\)
c) \(\left(3\dfrac{2}{9}.\dfrac{15}{23}.1\dfrac{7}{29}\right):\dfrac{5}{23}\)
\(=\left(\dfrac{29}{9}.\dfrac{15}{23}.\dfrac{36}{29}\right):\dfrac{5}{23}\)
\(=\dfrac{60}{23}:\dfrac{5}{23}\)
\(=12\)
a)=1/2 . 8/15 - 3/4.47/9
=4/15 - 47/12
=-73/20
b)=2-1/3 . -21/20
=2+7/20
=47/20
20 - 2.(x+4) = 4
2.(x+4) = 20 - 4
2.(x+4) = 16
x+4 = 16 : 2
x+4 = 8
x = 8 - 4
x = 4
2(x-1):3=43 + 23
2(x-1):3= 64 + 8
2(x-1):3= 72
2(x-1) = 72 x 3
2(x-1) = 216
x - 1 = 216 : 2
x - 1 = 108
x = 108 + 1
x = 109
Hok tốt !
20-2(x+4)=4
2(x+4)=20-4
2(x+4)=16
x+4=16:2
x+4=8
x=8:4
x=2
Vậy x=2
12(x-1):3=43+23
12(x+1):3=64+8
12(x+1):3=72
12(x+1)=72.3
12(x+1)=216
x+1=216:12
x+1=18
x=18-1
x=17
Vậy x=17