Giup minh giải câu 32 33
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mk viết lại đề nha
\(7\times5^2-32\div2^3+3^2\)
\(7\times25-2^5\div2^3+9\)
\(175-2^2+9\)
\(175-4+9\)
\(180\)
tk mk nha bn____________!!
7 x 25 - 25 : 23 + 9
175 - 22 + 9
175 - 4 + 9
= 180
Đáp án đúng là : 180
tk to nha
36.
\(Q=x-2+\dfrac{3}{x-2}+2\ge2\sqrt{\dfrac{3\left(x-2\right)}{x-2}}+2=2\left(\sqrt{3}+1\right)\)
39.
\(\dfrac{\sqrt{3}cosx+sinx}{2cosx+3sinx}=\dfrac{\dfrac{\sqrt{3}cosx}{sinx}+\dfrac{sinx}{sinx}}{\dfrac{2cosx}{sinx}+\dfrac{3sinx}{sinx}}=\dfrac{\sqrt{3}cotx+1}{2cotx+3}=\dfrac{\sqrt{3}.\left(-\dfrac{1}{2}\right)+1}{2.\left(-\dfrac{1}{2}\right)+3}=\dfrac{2-\sqrt{3}}{4}\)
\(\Rightarrow\left\{{}\begin{matrix}a=2\\b=1\end{matrix}\right.\) \(\Rightarrow a-4b=-2\)
40. \(\overrightarrow{BA}=\left(6;4\right)=2\left(3;2\right)\Rightarrow\) trung trực AB nhận (3;2) là 1 vtpt
Gọi M là trung điểm AB \(\Rightarrow M\left(-1;3\right)\)
Phương trình trung trực AB:
\(3\left(x+1\right)+2\left(y-3\right)=0\Leftrightarrow3x+2y-3=0\)
S = 1 + 3 + 32 + 33 + ... + 359
S = ( 1 + 3 + 32 ) + ( 33 + 34 + 35 ) + ... + ( 357 + 358 + 359 )
S = 13 + 33( 1 + 3 + 32 ) + ... + 357( 1 + 3 + 32 )
S = 13 + 33 . 13 + ... + 357 . 13
S = 13 ( 1 + 33 + ... + 357 ) ⋮ 13 vì 13 ⋮ 13
Vậy S ⋮ 13
\(S=1.\left(1+3\right)+3^2\left(1+3\right)+3^4\left(1+3\right)+...+3^8\left(1+3\right)\)
\(S=4x\left(1+3^2+...+3^8\right)\)
Vì 4 chia hết cho 4 nên S chia hết cho 4
33. He didn't know where to find more information about that.
34. The teacher says that I'm the noisiest student in the school.
35. The city hasn't changed since the 1990s.
36. He is used to drinking coffee in the morning.
29, independence
30,inventors
31,Disneyland has attracted over 670 million people since it opened in 1955
32,The house reicive energy of the sun from the solar panels are installed on the roof
33,He didn't know where he can find more information about that
34,The teacher says that I'm the noisiest student in the school
35,The city hasn't changed since it was in 1990s
36,He is used to drinking coffe in the morning
32.
\(sin^4x=\left(sin^2x\right)^2=\left(\dfrac{1-cos2x}{2}\right)^2=\dfrac{1}{4}-\dfrac{1}{2}cos2x+\dfrac{1}{4}cos^22x\)
\(\)\(=\dfrac{1}{4}-\dfrac{1}{2}cos2x+\dfrac{1}{4}\left(\dfrac{1}{2}+\dfrac{1}{2}cos4x\right)\)
\(=\dfrac{3}{8}-\dfrac{1}{2}cos2x+\dfrac{1}{8}cos4x\)
\(a+b+2c=\dfrac{3}{8}-\dfrac{1}{2}+2.\left(\dfrac{1}{8}\right)=\dfrac{1}{8}\)
33.
\(\Leftrightarrow\left\{{}\begin{matrix}m>0\\\Delta=m^2-4m< 0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}m>0\\0< m< 4\end{matrix}\right.\)
\(\Rightarrow m=\left\{1;2;3\right\}\) có 3 giá trị