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Câu hỏi của Solyver - Toán lớp 7 - Học toán với OnlineMath
a: Ta có: ΔABC cân tại A
mà AH là đường cao
nên H là trung điểm của BC
=>BH=CH=BC/2=6cm
=>AH=8cm
b: Xét ΔABC có
BI là đường trung tuyến
AH là đường trung tuyến
BI cắt HA tại G
Do đó: G là trọng tâm của ΔABC
=>HG=1/3AH=8/3(cm)
c: Ta có: G là trọng tâm của ΔABC
nên CG là đường trung tuyến ứng với cạnh AB
mà K là trung điểm của AB
nên C,G,K thẳng hàng
\(\lim\dfrac{3^n+2.6^n}{6^{n-1}+5.4^n}=\lim\dfrac{6^n\left[\left(\dfrac{3}{6}\right)^n+2\right]}{6^n\left[\dfrac{1}{6}+5\left(\dfrac{4}{6}\right)^n\right]}=\lim\dfrac{\left(\dfrac{3}{6}\right)^n+2}{\dfrac{1}{6}+5\left(\dfrac{4}{6}\right)^n}=\dfrac{0+2}{\dfrac{1}{6}+0}=12\)
\(\lim\left(\sqrt{n^2+9}-n\right)=\lim\dfrac{\left(\sqrt{n^2+9}-n\right)\left(\sqrt{n^2+9}+n\right)}{\sqrt{n^2+9}+n}=\lim\dfrac{9}{\sqrt{n^2+9}+n}\)
\(=\lim\dfrac{n\left(\dfrac{9}{n}\right)}{n\left(\sqrt{1+\dfrac{9}{n^2}}+1\right)}=\lim\dfrac{\dfrac{9}{n}}{\sqrt{1+\dfrac{9}{n^2}}+1}=\dfrac{0}{1+1}=0\)
\(\lim\dfrac{\sqrt{15+9n^2}-3}{5-n}=\lim\dfrac{n\sqrt{\dfrac{15}{n^2}+9}-3}{5-n}=\lim\dfrac{n\left(\sqrt{\dfrac{15}{n^2}+9}-\dfrac{3}{n}\right)}{n\left(\dfrac{5}{n}-1\right)}\)
\(=\lim\dfrac{\sqrt{\dfrac{15}{n^2}+9}-\dfrac{3}{n}}{\dfrac{5}{n}-1}=\dfrac{\sqrt{9}-0}{0-1}=-3\)
I
2 Did your mum make
3 doesn't work
4 didn't come
5 don't visit
6 Did Julia weat
7 do
8 sent
II
2 wasn't
3 went
4 go
5 Did you have
6 had
7 Did you stay
8 stayed
9 Do they live
10 is
11 walked - swam
III
1 Her
2 They
3 Their
4 It
5 Her
6 it
7 it
IV
1 B
2 A
3 B
4 B
5 C
6 A
7 C
8 B
9 A
10 C
11 B
12 B
13 C
14 B
15 A
Grade 8
I
2 slept
3 opened
4 ironed
5 cleaned
6 taken
7 arrived
8 put
9 left
10 broken
11 made
12 run
II
2 haven't eaten
3 have bought
4 hasn't brushed
5 has sent
6 haven't seen
7 has been
8 has visited
9 have done
10 hasn't had
III
1 yet
2 yesterday
3 already
4 never
5 last weekend
6 three days ago
8 so far
9 recently
IV
2 A
3 C
4 A
4 C
6 B
7 always likes
8 A
9 B
10 B
V
2 haven't played - has been
3 have visited - went
4 Have you chosen - bought
5 have you seen - watched
6 has forgot - didn't say
7 has broken - fell
8 Have you sold - saw - bought
9 have finished - painted - put up
10 have lost - ran