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a) 91.25 - 91.13 - 91.12 = 91.(25 - 13 - 12) = 0;
b) 47.8 - 27.9 + 47.12 - 27.11 = 47. (8 +12) - 27.(9 +11)
= (47-27).20 = 400;
c) 236 : 3 + 64 : 3 = (236 + 64) : 3 = 100;
d) 375 : 25 - 125 : 25 = (375 - 125) : 25 = 10
Bài 3 :
A = 26 + 27 + 28 + 29 + 30 + 31 + 32 + 33
=> A = ( 33 + 26 ) . 8 : 2 = 236
Vậy A = 236
\(\text{#Hok tốt!}\)
a) 2 . 31 . 12 + 4 . 6 . 42 + 8 . 27 . 3
= 24 . 31 + 24 . 42 + 24 . 27
= 24 . ( 31 + 42 + 27 )
= 24 . 100
= 2400
\(\frac{2^8\times6}{3^3\times5^4}\div\frac{8^3\times9}{5^3\times3^3}-\left(2^{14}+3^{19}\right)\left(3^{81}+5^{64}\right)\left(2^4-4^2\right)\)
\(=\frac{2^9\times3}{3^3\times5^4}\times\frac{5^3\times3^3}{2^9\times3^2}-\left(2^{14}+3^{19}\right)\left(3^{81}+5^{64}\right)\left(2^4-2^4\right)\)
\(=\frac{2^9\times3^4\times5^3}{3^5\times5^4\times2^9}-\left(2^{14}+3^{19}\right)\left(3^{81}+5^{64}\right)\times0\)
\(=\frac{1}{3\times5}-0\)
\(=\frac{1}{15}\)
3.Tìm x biết:
a) \(2-x=17-\left(-5\right)\)
\(2-x=22\)
\(x=2-22\)
\(x=-20\)
Vậy \(x=-20\)
b) \(2x-6=-3-\left(-7\right)\)
\(2x-6=4\)
\(2x=6+4\)
\(2x=10\)
\(x=10:2\)
\(x=5\)
Vậy \(x=5\)
c) \(\left(3x-6\right).3=3^4\)
\(\left(3x-6\right).3=81\)
\(3x-6=81:3\)
\(3x-6=27\)
\(3x=27+6\)
\(3x=33\)
\(x=33:3\)
\(x=11\)
Vậy \(x=11\)
\(-0,8\cdot1\frac{9}{25}-\frac{4}{5}\cdot\frac{64}{25}\)
\(=\frac{-4}{5}\cdot\frac{34}{25}+\frac{-4}{5}\cdot\frac{64}{25}\)
\(=\frac{-4}{5}\left(\frac{34}{25}+\frac{64}{25}\right)\)
\(=\frac{-4}{5}\cdot\frac{98}{25}\)
\(=\frac{-392}{125}\)
Chắc sai =))
\(\frac{\frac{1}{3}+\frac{1}{7}-\frac{1}{13}}{\frac{2}{3}+\frac{4}{14}-\frac{2}{13}}\times\frac{\frac{3}{4}-\frac{3}{16}+\frac{3}{64}-\frac{3}{256}}{1-\frac{1}{4}+\frac{1}{16}-\frac{1}{64}}+\frac{5}{8}\)
\(=\frac{\frac{2}{6}+\frac{2}{14}-\frac{2}{26}}{\frac{4}{6}+\frac{4}{14}-\frac{4}{26}}\times\frac{\frac{3}{4}-\frac{3}{16}+\frac{3}{64}-\frac{3}{356}}{\frac{4}{4}-\frac{4}{16}+\frac{4}{64}-\frac{4}{256}}+\frac{5}{8}\)
\(=\frac{2\left(\frac{1}{6}+\frac{1}{14}-\frac{1}{26}\right)}{4\left(\frac{1}{6}+\frac{1}{14}-\frac{1}{26}\right)}\times\frac{3\left(\frac{1}{4}-\frac{1}{16}+\frac{1}{64}-\frac{1}{356}\right)}{4\left(\frac{1}{4}-\frac{1}{16}+\frac{1}{64}-\frac{1}{256}\right)}+\frac{5}{8}\)
\(=\frac{2}{4}\times\frac{3}{4}+\frac{5}{8}\)
\(=\frac{1}{2}\times\frac{3}{4}+\frac{5}{8}\)
\(=\frac{3}{8}+\frac{5}{8}\)
\(=\frac{8}{8}=1\)
\(\frac{\frac{109}{3.7.13}}{\frac{361}{3.14.13}}\)\(\frac{\frac{153}{256}}{\frac{51}{64}}\)+5/8
=\(\frac{327}{722}\)+5/8
=\(\frac{3113}{2888}\)
236 : 3 + 64 : 3 = (236 + 64) : 3 = 100