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\(\sqrt{\sqrt{5}-\sqrt{3-\sqrt{29-12\sqrt{5}}}}\)
=\(\sqrt{\sqrt{5}-\sqrt{3-\sqrt{3^2-12\sqrt{5}+\left(2\sqrt{5}\right)^2}}}\)
\(=\sqrt{\sqrt{5}-\sqrt{3-\left(3-2\sqrt{5}\right)^2}}\)
\(=\sqrt{\sqrt{5}-\sqrt{6-2\sqrt{5}}}\)
\(=\sqrt{\sqrt{5}-\sqrt{5-2\sqrt{5}+1}}\)
=\(\sqrt{\sqrt{5}-\sqrt{\left(\sqrt{5}-1\right)^2}}\)
\(=\sqrt{\sqrt{5}-\sqrt{5}+1}\)
\(=\sqrt{1}=1\)
k
\(\sqrt{117,5^2-26,5^2-1440}\)\(=\sqrt{\left(117,5-26.5\right)\left(117.5+26,5\right)-144\cdot10}\)\(=\sqrt{91\cdot144-144\cdot10}\)
\(=\sqrt{144\cdot\left(91-10\right)}\)
\(=\sqrt{144\cdot81}\)
\(=\sqrt{144}\cdot\sqrt{81}\)
\(=12\cdot9=108\)
\(\dfrac{\sqrt{xy^3}\cdot\sqrt{x^2-y^2}}{\sqrt{\left(x+y\right)\left(x^2y^3-xy^4\right)}}\)
\(=\dfrac{\sqrt{xy^3}\cdot\sqrt{\left(x+y\right)\left(x-y\right)}}{\sqrt{\left(x+y\right)\cdot xy^3\left(x-y\right)}}\)
\(=\dfrac{\sqrt{xy^3}\cdot\sqrt{x+y}\cdot\sqrt{x-y}}{\sqrt{x+y}\cdot\sqrt{xy^3}\cdot\sqrt{x-y}}\)
\(=1\)
\(\sqrt{6+2\sqrt{5}}:\left(1+\sqrt{5}\right)\)
\(=\sqrt{5+2\cdot\sqrt{5}+1}:\left(1+\sqrt{5}\right)\)
\(=\sqrt{\left(\sqrt{5}+1\right)^2}:\left(1+\sqrt{5}\right)\)
= \(\left(\sqrt{5}+1\right):\left(1+\sqrt{5}\right)=1\)
mạch nt hay song song
có sơ đồ ko
vì 2 dây cùng chất liệu nên
\(\rho_1=\rho_2\)
\(\Rightarrow\dfrac{R_1S_1}{l_1}=\dfrac{R_2S_2}{l_2}\)
\(\Rightarrow S_2=\dfrac{R_1S_1l_2}{R_2l_1}=\dfrac{15\cdot0,2\cdot10^{-6}\cdot30}{10\cdot24}\)
\(=0,375\cdot10^{-6}m^2\)
hay 0,375\(mm^2\)
ta có R=\(\rho\dfrac{l}{s}\)
\(\Rightarrow\rho=\dfrac{R\cdot S}{l}=\dfrac{7\cdot0,4\cdot10^{-6}}{100}=2,8\cdot10^{-8}\left(\Omega m\right)\)
quãng đường tàu đi được là S=v.t=30.5=150(km)