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18 tháng 12 2016

Đặt \(a=\frac{1-\sqrt{5}}{2},b=\frac{1+\sqrt{5}}{2}\)

Ta có \(a+b=1,a-b=-\sqrt{5},ab=-1\)

Ta sẽ tính từ từ. Cụ thể

\(a^2+b^2=\left(a+b\right)^2-2ab=3\)

\(a^2-b^2=\left(a+b\right)\left(a-b\right)=-\sqrt{5}\)

\(a^4+b^4=\left(a^2+b^2\right)^2-2\left(ab\right)^2=7\)

\(a^4-b^4=\left(a^2+b^2\right)\left(a^2-b^2\right)=-3\sqrt{5}\)

\(a^8+b^8=\left(a^4+b^4\right)^2-2\left(ab\right)^4=47\)

\(a^8-b^8=\left(a^4+b^4\right)\left(a^4-b^4\right)=-21\sqrt{5}\)

\(a^{16}-b^{16}=\left(a^8+b^8\right)\left(a^8-b^8\right)=-987\sqrt{5}\)

\(b,\left(\sqrt{1\frac{9}{16}-\sqrt{\frac{9}{16}}}\right):5\)

\(=\left(\sqrt{\frac{25}{16}-\frac{3}{4}}\right):5\)

\(=\sqrt{\frac{13}{16}}:5\)

\(=\frac{\sqrt{13}}{4}:5\)

\(=\frac{\sqrt{13}}{20}\)

13 tháng 8 2016

\(\left(\frac{2}{5}\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}=\left(\frac{2}{5}.\sqrt{4^2}+2\sqrt{\frac{4^2}{5^2}}\right):\frac{2}{\sqrt{4^2}}\)

\(=\left(\frac{2}{5}.4+2.\frac{4}{5}\right).2=\left(\frac{8}{5}+\frac{8}{5}\right).2=\frac{32}{5}\)

13 tháng 8 2016

\(\left(\frac{2}{5}.\sqrt{16}+2\sqrt{\frac{16}{25}}\right):2\sqrt{\frac{1}{16}}\)

\(=\left(\frac{2}{5}.4+2.\frac{4}{5}\right):2.\frac{1}{4}\)

\(=\left(\frac{8}{5}+\frac{8}{5}\right):\frac{1}{2}\)

\(=\frac{16}{5}:\frac{1}{2}\)

\(=\frac{32}{5}\)

hihi ^...^ vui^_^

21 tháng 10 2018

a) = \(\frac{7}{2}\)

b) = \(\frac{643}{64}\)

c) = 0

a) \(\frac{-6}{21}.\frac{3}{2}=-\frac{3}{7}\)          b) \(\left(-3\right).\left(\frac{-7}{12}\right)=\frac{21}{12}=\frac{7}{4}\)

c) \(\left(\frac{11}{12}:\frac{33}{16}\right).\frac{3}{5}=\frac{11}{12}.\frac{16}{33}.\frac{3}{5}=\frac{4}{15}\)

d) \(\sqrt{\left(-7\right)^2}+\sqrt{\frac{2}{16}}=7+\sqrt{\frac{1}{8}}\)

c) \(\frac{1}{2}.\sqrt{100}-\sqrt{\frac{1}{16}}+\left(\frac{1}{3}\right)^0=\frac{1}{2}.10-\frac{1}{4}+1=5\frac{3}{4}\)

10 tháng 3 2020

d) \(\left(-45,7\right)+\left[\left(+5,7\right)+\left(+5,75\right)+\left(-0,75\right)\right]\)

\(=\left(-45,7\right)+\left[5,7+5,75-0,75\right]\)

\(=\left(-45,7\right)+5,7+5,75-0,75\)

\(=\left[\left(-45,7+5,7\right)\right]+\left[5,75-0,75\right]\)

\(=-40+5=-35\)

e) \(11,26-5,13:\left(5\frac{5}{18}-1\frac{8}{9}\cdot1,25+1\frac{16}{63}\right)\)

\(=11,26-5,13:\left(\frac{95}{18}-\frac{17}{9}\cdot\frac{5}{4}+\frac{79}{63}\right)\)

\(=11,26-5,13:\left(\frac{95}{18}-\frac{85}{36}+\frac{79}{63}\right)\)

\(=\frac{563}{50}-\frac{513}{100}:\frac{1051}{252}\)

\(=\frac{563}{50}-\frac{513}{100}\cdot\frac{252}{1051}\)

\(=\frac{563}{50}-\frac{129276}{105100}=\frac{21083}{2102}\)

Số lớn quá!

j) \(\sqrt{8^2+6^2}\cdot\sqrt{16}+\frac{1}{2}\cdot\sqrt{\frac{4}{5}}\)

\(=\sqrt{64+36}\cdot\sqrt{16}+\frac{1}{2}\cdot\sqrt{\frac{4}{5}}\)

\(=\sqrt{100}\cdot4+\frac{1}{2}\cdot\frac{2\sqrt{5}}{5}\)

\(=10\cdot4+\frac{\sqrt{5}}{5}=40+\frac{\sqrt{5}}{5}=\frac{200+\sqrt{5}}{5}\)

h) Cái đây mình có làm rồi