15 m 65 cm = 15,65 m

Độ dài cạnh 3 là:

(12,35 + 15,65) : 2 = 14 (m)

Chu vi tam giác là:

12,35 + 15,65 + 14 = 42 (m)

Đáp số : 42 m

1. I usually go to work with a friend, but yesterday i drove to work by himself because he was ill

* himself >> myself

2. alex doesn't have to take his medicine yesterday bacause he was better

* doesn't >> didn't

3.it is not safe leaving small objects around the house

* leaving >> to leave

4. it is dangerous not to cover electricity

* not to >> to not

5. he left a note for you above the chicken table

* above >> on

tik mik nha !!!

1.

a) \(2\left(x+3\right)-x^2-3x=0\)

\(2\left(x+3\right)-\left(x^2+3x\right)=0\)

\(2\left(x+3\right)-x\left(x+3\right)=0\)

\(\left(2-x\right)\left(x+3\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}2-x=0\\x+3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)

Vậy x=2 hoặc x=-3

b) \(8x^3-50x=0\)

\(x\left(8x^2-50\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=0\\8x^2-50=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x^2=\dfrac{25}{4}=\left(\pm\dfrac{5}{2}\right)^2\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{5}{2}\\x=\dfrac{-5}{2}\end{matrix}\right.\)

Vậy \(x=0\) hoặc \(x=\dfrac{-5}{2}\) hoặc \(x=\dfrac{5}{2}\)

tik mik nhé !!!

\(\left(-a^2\right)=a^2\) bạn nhé !!!

tik mik nhé !!

\(\left(x-y-7\right)^2+\left(4x-3y-24\right)^2=0\)

Nhận xét: \(\left(x-y-7\right)^2\ge0\) với \(\forall x,y\)

\(4x-3y-24\ge0\) với \(\forall x,y\)

\(\Rightarrow\left\{{}\begin{matrix}\left(x-y-7\right)^2=0\\\left(4x-3y-24\right)^2=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x-y-7=0\\4x-3y-24=0\end{matrix}\right.\)\(\Rightarrow4x-3y=24\Rightarrow4x=24+3y=3\left(y+8\right)\)

\(\Rightarrow\dfrac{x}{3}=\dfrac{y+8}{4}\) và \(x-y=7\)

Theo t/c dãy tỉ số bằng nhau, ta có :

\(\dfrac{x}{3}=\dfrac{y+8}{4}=\dfrac{x-y-8}{3-4}=\dfrac{7-8}{3-4}=1\)

\(\Rightarrow x=1.3=3\)

\(y+8=1.4=4\Rightarrow y=-4\)

tik mik nha !!!

1.

a) Để \(\overline{71x1y}⋮5\)(\(x,y\in N,\left(0\le x,y\le9\right)\))

=> \(\left[{}\begin{matrix}y=0\\y=5\end{matrix}\right.\)

Để \(\overline{71x1y}⋮9\Rightarrow\left(7+1+x+1+y\right)⋮9\)

hay \(9+x+y⋮9\)

* Nếu y=0

=> \(9+x⋮9\Rightarrow\left[{}\begin{matrix}x=0\\x=9\end{matrix}\right.\)

* Nếu y=5

=> \(14+x⋮9\Rightarrow x=5\)

Vậy các cặp số (x,y) t/m: (0,0);(9,0);(5,5).

câu b bạn làm tương tự là đc bạn nhé !!!

tk mik nhé !!!

Để \(\overline{517xy}⋮9\Rightarrow\left(5+1+7+x+y\right)⋮9\)

1. The picture is very expensive .

-> What an expensive picture !

2. Nobody in Nga's class is better than she is .

-> Nga is the best student in her class

tik mik nha !!!

bn tick mk đi mk làm cho

1.

a) Ta có \(A=2+2^2+...+2^{10}\)

\(2A=2^2+2^3+2^4+...+2^{10}+2^{11}\)

\(A=2A-A=2^{11}-2\)

thay \(A=2^{11}-2\) vào \(A+2=2^x\) ta có :

\(2^{11}-2+2=2^x\)

=> \(2^{11}=2^x\) \(\Rightarrow x=11\)

Vậy x=11

tik mik nha

 Vì x²>_0

     |x+3/4|>_0

=>x²+|x+3/4|>_0

=>|x²+|x+3/4||=x²+|x+3/4|

=>x²+|x+3/4|=x²

=>|x+3/4|=x²-x²

=>|x-3/4|=0

=>x-3/4=0

=>x=3/4

 Vì x²>_0

     |x+3/4|>_0

=>x².|x+3/4|>_0

=>|x².|x+3/4||=x²+|x+3/4|

=>x².|x+3/4|=x²

=>|x.3/4|=x²:x²

=>|x-3/4|=1

=>x-3/4=-1,1

=>x=-1/4,7/4

Vậy .............

tick nhé