Mn ơi, cíu mk
K
Khách
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cíu bé vs mn ơi
Y
6 tháng 10 2023
\(A=\left\{x\in Z|\left(x^2-9\right)\left(x^2-7\right)\left(3x+5\right)=0\right\}\)
Giải pt \(\left(x^2-9\right)\left(x^2-7\right)\left(3x+5\right)=0\) \(\left(dk:x\in Z\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-9=0\\x^2-7=0\\3x+5=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=\pm3\left(tm\right)\\x=\pm\sqrt{7}\left(ktm\right)\\x=-\dfrac{5}{3}\left(ktm\right)\end{matrix}\right.\)
Vậy \(A=\left\{-3;3\right\}\)
Cíu mình dới mn ơi huhu
ND
2
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
9 tháng 1
(-5)3.\(x^2\) = - 1125
\(x^2\) = (-1125) : (-53)
\(x^2\) = 9
\(\left[{}\begin{matrix}x=-3\\x=3\end{matrix}\right.\)
Vậy \(x\) \(\in\) {-3; 3}
DM
1
DT
Đỗ Thanh Hải
CTVVIP
15 tháng 10 2021
1 lived
2 wasn't hearing - was thinking
3 walked - was
4 were you doing - phoned
5 was reading - heard
6 was walking - saw
7 had watched - wrote
8 met
9 had you done - moved
10 was - didn't attend
II
1 when we were having lunch
2 had read the instruction, I started the machine
3 went out for a rest, we had finished our assignment
4 she left, it was raining
5 learning English
6 to help me
7 the man to open the briefcase
8 my friend break the bottle
9 him fall off the bike
10 a foreign language in a short time is not easy
9 tháng 8 2023
cos2A+cos2B-cos2C
=2*cos(A+B)*cos(A-B)-2cos^2C+1
=-2*cosC+cos(A-B)-2cos^2C+1
=-2*cosC[cos(A-B)+cosC]+1
=-2*cosC[cos(A-B)-cos(A+B)]+1
=\(=2\cdot cosC\cdot2\left[sin\left(\dfrac{A-B+A+B}{2}\right)\cdot sin\left(\dfrac{A-B-A-B}{2}\right)\right]+1\)
\(=-4\cdot cosC\cdot\left[sinA\cdot sinB\right]+1\)
=>\(1-4\cdot sinA\cdot sinB\cdot cosC\)(ĐPCM)
Cíu!!!!! Mn ơi giải thích cho em trường hợp này là như nào ạ!!!!!
Câu 7: D
Câu 8: B
Câu 9: B
1,D
2,B
3,B