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Ta có 4+6+n+7+4+2=30 suy ra n=7
b) \(7=\frac{4.5+6.6+7.7+8.7+x.4+10.2}{30}\)
suy ra 210=20+36+49+56+4x+20
4x=210-181
4x=29
câu 1: cho 2x+8=0
(=) x=-4
câu 2 x=-6
câu 3 x=0 hoặc x=2
NHỚ CHỌN ĐẤY
2x+8=0 suy ra 2x=-8 suy ra x=-4
b) 1/2x+3=0 suy ra 1/2x=-3 suy ra x=-6
c) x.x-2.x=0 suy ra x.(x-2)=0 suy ra x=0 hoặc x-2=0
suy ra x=0 hoặc x=2
Vậy x thuộc {0;2}
1. Viết 1 đoạn văn kể về kỳ nghỉ của em bằng tiếng anh ( khoảng 7 - 8 câu )
Last Summer Holiday I went to Ha Long Bay with my family . We went there by plane . First , we took a boat trip around the island. In the morning , I and my brother swam in the sea and built sandcastle on the beach . In the afternoon we went to Tuan Chau Island to see water pupets and then I had seafood in the big restaurant . In the evening , we went for a walk along the seaside . It was a wonderful holiday last summer .
2. Viết 1 đoạn văn kể về 1 ngày của em bằng tiếng anh ( khoảng 7 - 8 câu )
every day I usually get up early . I brushed my teeth and wash my face . then I do morning exercise with my parents .after that I have breakfast at home , then I get dressed and go to school . In the afternoon, I had lunch at the school canteen . after school I play table tennis with my father .I have dinner with my family at home. After dinner, I usually listen to music before going to bed. I love my day very much
Đề 3 bạn tự làm nhé
Học tốt !
a) Ta có \(P=x+\sqrt{x}+1\)(đkxđ:\(x\ge0\))
Với \(x\ge0\Rightarrow P=x+\sqrt{x}+1\ge0\)
Vậy P đạt GTNN là 0 khi x=0
b) Ta có \(2^a+7=|b-5|+b-5\)
TH1 \(|b-5|=b-5\)
\(\Rightarrow2^a+7=b-5+b-5\)
\(\Leftrightarrow2^a=2b-17\)(1)
Vì \(2^a\)chẵn mà \(2b-17\)lẻ nên suy ra (1) vô lí
TH2 \(|b-5|=5-b\)
\(\Rightarrow2^a+7=5-b+b-5\)
\(\Leftrightarrow2^a+7=0\Leftrightarrow2^a=-7\)(2)
Vì \(2^a\)chẵn mà -7 lẻ nên suy ra (2) vô lí
Vậy không có giá trị nào của a và b thỏa mãn \(2^a+7=|b-5|+b-5\)
A = |x + 2| + |x - 3|
|x + 2| > x + 2
|x - 3| > 3 - x
=> A > x + 2 + 3 - x
=> A > 5
xét A = 5 khi
x + 2 > 0 và x - 3 < 0
=> x > 2 và x < 3
=> 2 < x < 3
=> x = 2
vậy min A = 5 khi x = 2
Áp dụng bất đẳng thức \(\left|a\right|+\left|b\right|\ge\left|a+b\right|\) , ta có :
\(A=\left|x+2\right|+\left|x-3\right|=\left|x+2\right|+\left|3-x\right|\ge\left|x+2+3-x\right|=5\)
Còn lại lm nốt nha
tam giác OAH=tam giác RAH
20. Wait for few minutes, please! I am finishing my dinner.
21. Have you ever eat Sushi?
22. She didn't come here for a long time.
23. I have worked here for three years.
24. Have you ever been to New York?
25. You haven't do your project yet, I suppose.
26. I cooked dinner at 6p.m yesterday.
27. I have just decided to start working next week.
29. She didn't have any fun a long time ago.
30. My father didn't played any sport since last year.
20. Wait for few minutes, please! I have finished my dinner.
21. Have you ever ate Sushi?
22. She hasn't come here for a long time.
23. I have worked here for three years.
24. Have you ever been to New York?
25. You haven't done your project yet, I suppose.
26. I cooked dinner at 6 p.m yesterday.
27. I have just decided to start working next week.
29. She didn't have any fun a long time ago.
30. My father haven't played any sport since last year.
#LamThy