tính :
[( 10-2.3).5]ư+2-2.6}:2+(4.5)2
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a) -(-239) + (-27) + (-215) - 121 = - 124
b) ((( 10 - 2.3) .5) + 2 - 2.6) :2 + (4.5) mũ 2 = 416
\(\frac{2}{1.2}+\frac{2}{2.3}+\frac{2}{3.4}+....+\frac{2}{19.20}\)
\(=2.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{19.20}\right)\)
\(=2.\left(1-\frac{1}{20}\right)\)
\(=2.\frac{19}{20}=\frac{19}{10}\)
\(\frac{2}{1.2}+\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+...+\frac{2}{19.20}\)
\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{20}\)
\(=\frac{1}{1}-\frac{1}{20}\)
\(=\frac{19}{20}\)
a) \(\left[\left(10-2.30.5\right)+2.6\right]:2+\left(4.5\right)^2\)
\(=\left[\left(10-300\right)+2.6\right]:2+20^2\)
\(=\left(-290+2.6\right):2+400\)
\(=\left(-290+12\right):2+400\)
\(=-278:2+400\)
\(=-139+400\)
\(=-\left(139-400\right)\)
\(=-\left(-261\right)\)
\(=261\)
b) \(536.27-9\left(825+219\right):18+15^3:15^2.4^2.3\)
\(=536.27-9.1044:18+15^3:15^2.4^2.3\)
\(=14472-9396:18+15^3:15^2.4^2.3\)
\(=14472-522+15^3:15^2.4^2.3\)
\(=13920+15^{3-2}.4^2.3\)
\(=13920+15.4^2.3\)
\(=13920+15.16.3\)
\(=13920+240.3\)
\(=13920+720\)
\(=14640\)
a) \(\dfrac{27^3\cdot11+9^5\cdot5}{3^9\cdot2^4}\)
\(=\dfrac{3^9\cdot11+3^{10}\cdot5}{3^9\cdot2^4}\)
\(=\dfrac{3^9\cdot\left(11+3\cdot5\right)}{3^9\cdot2^4}\)
\(=\dfrac{11+15}{16}\)
\(=\dfrac{26}{16}\)
\(=\dfrac{13}{8}\)
b) \(\dfrac{5^8+2^2\cdot25^4+2^3\cdot125^3-15^4\cdot5^4}{4^2\cdot625^2}\)
\(=\dfrac{5^8+2^2\cdot5^8+2^3\cdot5^9-3^4\cdot5^4\cdot5^4}{2^4\cdot5^8}\)
\(=\dfrac{5^8\cdot\left(1+2^2+2^3\cdot5-3^4\right)}{5^8\cdot2^4}\)
\(=\dfrac{1+4+40-81}{16}\)
\(=\dfrac{-36}{16}\)
\(=\dfrac{-9}{4}\)
c) \(\dfrac{4^5\cdot9^4-2\cdot6^9}{2^{10}\cdot3^8+6^8\cdot20}\)
\(=\dfrac{2^{10}\cdot3^8-2\cdot2^9\cdot3^9}{2^{10}\cdot3^8+2^{10}\cdot3^8\cdot5}\)
\(=\dfrac{2^{10}\cdot3^8\cdot\left(1-3\right)}{2^{10}\cdot3^8\cdot\left(1+5\right)}\)
\(=\dfrac{-2}{6}\)
\(=-\dfrac{1}{3}\)
A)3.5n.52+4.5n:53=19.9765625
5n(3.52+4:53)=185546875
5n.\(\frac{12}{5}\)=185546875