mn ơi giúp em cần gấp lắm ạ
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a: Xét ΔABM và ΔACM có
AB=AC
AM chung
BM=CM
Do đó:ΔABM=ΔACM
b: ta có: ΔABC cân tại A
mà AM là đường trung tuyến
nên AM là đường cao
c: BC=6cm
nên BM=3cm
=>AM=4cm
d: Xét ΔABC cân tại A có AM là đường cao
nên AM là phân giác của góc BAC
Xét ΔABC có
AM là đường phân giác
BI là đường phân giác
AM cắt BI tại I
Do đó: CI là tia phân giác của góc ACB
![](https://rs.olm.vn/images/avt/0.png?1311)
a, Vì D,M là trung điểm AB,AC nên DM là đtb tg ABC
Do đó \(DM=\dfrac{1}{2}BC=\dfrac{7}{2}\left(cm\right)\) và DM//BC
![](https://rs.olm.vn/images/avt/0.png?1311)
the sun rises in the east
water boils at 100 centigrade degrees
the weather is not warm enough to go swimming
I'd like to go on holiday but I haven't got enough money
he isn't experienced enough to do the job
the earth moves round the sun
I'm lucky enough to have a lot of friends
each of them has a different character
she has big brown eyes
his daughter has long blond hair
![](https://rs.olm.vn/images/avt/0.png?1311)
c. \(\left|\dfrac{8}{4}-\left|x-\dfrac{1}{4}\right|\right|-\dfrac{1}{2}=\dfrac{3}{4}\)
\(\Rightarrow\left[{}\begin{matrix}\left|\dfrac{8}{4}-x+\dfrac{1}{4}\right|-\dfrac{1}{2}=\dfrac{3}{4}\\\left|\dfrac{8}{4}+x-\dfrac{1}{4}\right|-\dfrac{1}{2}=\dfrac{3}{4}\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}\left|\dfrac{9}{4}-x\right|-\dfrac{1}{2}=\dfrac{3}{4}\\\left|\dfrac{7}{4}+x\right|-\dfrac{1}{2}=\dfrac{3}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}\dfrac{9}{4}-x-\dfrac{1}{2}=\dfrac{3}{4}\\x=\dfrac{9}{4}-\dfrac{1}{2}=\dfrac{3}{4}\end{matrix}\right.\\\left[{}\begin{matrix}\dfrac{7}{4}+x-\dfrac{1}{2}=\dfrac{3}{4}\\-\dfrac{7}{4}-x-\dfrac{1}{2}=\dfrac{3}{4}\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x=1\\x=\dfrac{7}{2}\end{matrix}\right.\\\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=-3\end{matrix}\right.\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{7}{2}\\x=-3\end{matrix}\right.\)
Ở nơi x=9/4-1/2 là x-9/4-1/2 nha
a. -1,5 + 2x = 2,5
<=> 2x = 2,5 + 1,5
<=> 2x = 4
<=> x = 2
b. \(\dfrac{3}{2}\left(x+5\right)-\dfrac{1}{2}=\dfrac{4}{3}\)
<=> \(\dfrac{3}{2}x+\dfrac{15}{2}-\dfrac{1}{2}=\dfrac{4}{3}\)
<=> \(\dfrac{9x}{6}+\dfrac{45}{6}-\dfrac{3}{6}=\dfrac{8}{6}\)
<=> 9x + 45 - 3 = 8
<=> 9x = 8 + 3 - 45
<=> 9x = -34
<=> x = \(\dfrac{-34}{9}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 3:
Diện tích là:
\(15\cdot6=90\left(m^2\right)\)
Bài 3:
Gọi cd,cr lần lượt là a,b(m;a,b>0)
Áp dụng tc dtsbn:
\(\dfrac{b}{a}=\dfrac{2}{5}\Rightarrow\dfrac{a}{5}=\dfrac{b}{2}=\dfrac{2a+2b}{10+4}=\dfrac{42}{14}=3\\ \Rightarrow\left\{{}\begin{matrix}a=15\\b=6\end{matrix}\right.\\ \Rightarrow S_{hcn}=ab=90\left(m^2\right)\)
Bài 4:
Gọi cd,cr lân lượt là a,b(m;a,b>0)
Đặt \(\dfrac{a}{4}=\dfrac{b}{3}=k\Rightarrow a=4k;b=3k\)
\(ab=300\left(m^2\right)\\ \Rightarrow12k^2=300\\ \Rightarrow k^2=25\Rightarrow k=5\left(k>0\right)\\ \Rightarrow\left\{{}\begin{matrix}a=20\\b=15\end{matrix}\right.\)
Vậy ...
Bài 5:
Gọi số hs 7A,7B,7C,7D ll là a,b,c,d(hs;a,b,c,d∈N*)
Áp dụng tc dtsbn:
\(\dfrac{a}{11}=\dfrac{b}{12}=\dfrac{c}{13}=\dfrac{d}{14}=\dfrac{2b-a}{24-11}=\dfrac{39}{13}=3\\ \Rightarrow\left\{{}\begin{matrix}a=33\\b=36\\c=39\\d=42\end{matrix}\right.\)
Vậy ...
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=\dfrac{2x+6}{3x\left(x+3\right)}=\dfrac{2\left(x+3\right)}{3x\left(x+3\right)}=\dfrac{2}{3x}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
\(\left(4x+3\right)\left(3x^2+x-2\right)\left(2x^2-3x-5\right)=0\\ \Leftrightarrow\left(4x+3\right)\left(3x-2\right)\left(x+1\right)\left(2x-5\right)\left(x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{4}\\x=-1\\x=\dfrac{2}{3}\\x=\dfrac{5}{2}\end{matrix}\right.\\ \Leftrightarrow A=\left\{-1;-\dfrac{3}{4};\dfrac{2}{3};\dfrac{5}{2}\right\}\)
Câu 2:
\(\left(x^2-4\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\\x=3\end{matrix}\right.\Leftrightarrow A=\left\{-2;2;3\right\}\\ \left|5x\right|-11\le0\Leftrightarrow\left|5x\right|\le11\Leftrightarrow-11\le5x\le11\\ \Leftrightarrow-\dfrac{11}{5}\le x\le\dfrac{11}{5}\\ \Leftrightarrow B=\left[-\dfrac{11}{5};\dfrac{11}{5}\right]\)
\(\Leftrightarrow A\cap B=\left\{-2;2\right\}\\ A\cup B=\left[-\dfrac{11}{5};3\right]\\ A\B=\left\{3\right\}\)
Refer
1 my sister is old. she can driver a car
=> My sister is old enough to drive a car
2 the ladder wasn't verry long .it didn't reach the ceiling
=> The ladder wasn't long enough to reach the ceiling
3 the fire isn't very hot. it won't boil a kettle
=> The fire isn't hot enough to boil a kettle
4 he is strong. he can carry that suicase
=> He is strong enough to carry that suitcase
5 Lan isn't strong . she can't swim across the rive
=> Lan isn't strong enough to swim across the river
6 she is beautiful and intelligent . she can become Miss World
=> She is beautiful and intelligent enough to become Miss World
7 MrRobert isn't rich he can't buy a house
=> Mr Robert isn't rich enough to buy a house
8 the worker in very clever . he can make nice things from wood
=> The worker is clever enough to make nice things from wood
9 our team is very good . we win the foodball match very often
=> Our team is good enough to win the football match very often
10 the radio isn't small . it can't be put it in your pocket
=> The radio isn't small enough to put in your pocket