Ý bn là ⋮ đúng không?

Chia hết

\(⋮\)

đẹp lắm bn nà

cũng duck đó e!!!

Cx dc

Tk tôi nhé

Tôi 2k4

Kb nhé

Bài 3:

a. \(R=p\dfrac{l}{S}=1,1.10^{-6}\dfrac{30}{0,2.10^{-6}}=165\Omega\)

b. \(Q=UIt=220\left(\dfrac{220}{165}\right).15.60=254000\left(J\right)\)

Bài 2:

a. \(R=\dfrac{U^2}{P}=\dfrac{220^2}{1000}=48,4\Omega\)

b. \(Q=UIt=220\left(\dfrac{220}{48,4}\right).4.3600=14400000\left(J\right)\)

c. \(Q'=Q.40=14400000.40=576000000\left(J\right)=120000\)kWh

\(\Rightarrow T=Q'.2100=120000.2100=252000000\left(dong\right)\)

Bài 1:

a. \(Q=UIt=220.2,5.1=550\left(J\right)\)

b. \(\left\{{}\begin{matrix}Q_{thu}=mc\left(t-t_1\right)=2.4200\left(100-20\right)=672000\left(J\right)\\Q_{toa}=UIt=220.2,5.15.60=495000\left(J\right)\end{matrix}\right.\)

\(\Rightarrow H=\dfrac{Q_{toa}}{Q_{thu}}100\%=\dfrac{495000}{672000}100\%\approx73,6\%\)

1: Ta có: \(\sqrt{81x^2}=6\)

\(\Leftrightarrow\left|9x\right|=6\)

\(\Leftrightarrow\left[{}\begin{matrix}9x=6\\9x=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{2}{3}\end{matrix}\right.\)

2: Ta có: \(\sqrt{4x^2}+\sqrt{9x^2}=10\)

\(\Leftrightarrow2\left|x\right|+3\left|x\right|=10\)

\(\Leftrightarrow\left|x\right|=2\)

hay \(\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)

3: Ta có: \(\sqrt{36x^2}-4=0\)

\(\Leftrightarrow\left|6x\right|=4\)

\(\Leftrightarrow\left[{}\begin{matrix}6x=4\\6x=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{2}{3}\end{matrix}\right.\)

Help me!!! :(

\(A=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{16}+\dfrac{1}{16}+...-\dfrac{1}{128}\)

\(A=1-\dfrac{1}{128}=\dfrac{127}{128}\)

10 điểm

Mình không hiểu gì hết ''^.^''

ko đăng câu hỏi linh tinh nha bn !!!!!

bn nên đọc nội quy đi nha 

chúc bn hok tốt nha

#vanh#

làm

......., kb và ib vs mik đê