Câu 1: C

Câu 6: B

Câu 7: A

Câu 12: B

a, \(\dfrac{23}{4}\)

d, \(\dfrac{27}{8}\)

a, 3/4 + 5 

 = 3/4 + 20/4

 = 23/4

b, 3 : 8/9

 = 3 x 9/8

 = 27/8

a) 3/4 + 5=3/4+20/4=23/4
d) 3 : 8/9 = 3 x 9/8= 3/8

\(\left(a-b\right)^2=a^2-2ab+b^2=144\\ \Leftrightarrow154-2ab=144\\ \Leftrightarrow ab=5\\ \Leftrightarrow M=\left(a-b\right)^3+3ab\left(a-b\right)=12^3+3\cdot5\cdot12=1908\)

Câu 11.

a)Độ tự cảm của ống dây:

\(L=4\pi\cdot10^{-7}\cdot\dfrac{N^2}{l}S=4\pi\cdot10^{-7}\cdot\dfrac{1000^2}{0,2}\cdot50\cdot10^{-4}=0,0314H=0,0314\cdot10^3=31,4mH\)

b)Độ biến thiên từ thông:

\(\Delta\Phi=L\cdot\Delta i=0,0314\cdot\left(1-0\right)=0,0314Wb\)

Suất điện động cảm ứng:

\(e_{tc}=\left|-\dfrac{\Delta\Phi}{\Delta t}\right|=\left|-\dfrac{0,0314}{0,1}\right|=0,314V\)

a: \(38\cdot76-38\cdot\left(-62\right)-\left(-38\right)^2\)

\(=38\cdot76+38\cdot62-38^2\)

\(=38\left(76+62-38\right)\)

\(=38\cdot100=3800\)

b: \(\left(-43-2265\right)-\left(157-3265\right)\)

\(=-43-2265-157+3265\)

\(=\left(-43-157\right)+\left(3265-2265\right)\)

=1000-200

=800

c: \(\dfrac{-5}{12}+\dfrac{3}{8}-\dfrac{5}{6}\)

\(=\dfrac{-10+9-20}{24}\)

\(=\dfrac{-21}{24}=\dfrac{-7}{8}\)

a: y:72,5=35,9

nên y=2602,75

b: =21,4

\(y:72,5=42,8-6,9.\\ \Leftrightarrow y:72,5=35,9.\\ \Leftrightarrow y=2602,75.\)

Lời giải:

\(H=2-\frac{3}{17}-\frac{5}{23}+\frac{2}{17}-\frac{1}{2023}-\frac{16}{17}-\frac{18}{23}\\ =2-(\frac{3}{17}-\frac{2}{17}+\frac{16}{17})-(\frac{5}{23}+\frac{18}{23})-\frac{1}{2023}\\ =2-1-1-\frac{1}{2023}=-\frac{1}{2023}\)

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\(K=\frac{7}{23}.\frac{-11}{17}+\frac{7}{23}.\frac{4}{17}-\frac{7}{23}.\frac{10}{17}\\ =\frac{7}{23}(\frac{-11}{17}+\frac{4}{17}-\frac{10}{17})\\ =\frac{7}{23}.\frac{-17}{17}=\frac{-7}{23}\)