Hình đâu bn?

Số góc 12 tia chung gốc  tạo thành là:

   \(\dfrac{n.\left(n-1\right)}{2}=\dfrac{12.\left(12-1\right)}{2}=66\) ( góc )

 Vậy có 66 góc được tạo bởi 12 tia chung gốc.

\(a,867+80-167\\ =\left(867-167\right)+80\\ =700+80\\ =780\\ b,235+137+265+363\\ =\left(137+363\right)+\left(235+265\right)\\ =500+500\\ =1000.\)

Ta có: 2 góc so le trong bằng nhau

\(\Rightarrow\) \(\dfrac{1}{2}\widehat{a_1}=\dfrac{1}{2}\widehat{b_1}\) .

Mà đường thẳng cắt 2 đường thẳng ban đầu lại cắt 2 tia phân giác đó trong đó có 1 cặp so le trong bằng nhau.

\(\Rightarrow\) 2 tia phân giác đó // với nhau.

\(\Rightarrow\) Ta được \(dpcm\) .

\(\left(xy+1\right).\left(x-7\right)=5\\ \Rightarrow\left(xy+1\right),\left(x-7\right)\in\left\{\left(1,5\right);\left(5,1\right)\right\}\\ \Rightarrow y,x\in\left\{\left(0,12\right);\left(2,8\right)\right\}\)

1. What is your mother doing?

2. What are Nam and Hung doing now?

3. Hanoi is going to that businessman.

4. Is he dring his truck?

5. Who is he waiting for?

6. Quang is driving to Hue.

7. He is  taking to the vegetables maket.

8. The train is going to Nha Trang.

9. The children are playing in the garden.

10.Mai is brushing her teeth.

\(\left[\left(6x^2-12\right):3\right]\times16=64\\ \left(6x^2-12\right):3=4\\ 6x^2-12=12\\ 6x^2=24\\ x^2=4\\ x^2=2^2\\ x=2.\)

\(230+\left[2^2+\left(x-5\right)^2\right]=315\times2021^0\\ 230+\left[4+\left(x-5\right)^2\right]=315\times1\\ 230+\left[4+\left(x-5\right)^2\right]=315\\ 4+\left(x-5\right)^2=85\\ \left(x-5\right)^2=81\\ \left(x-5\right)^2=9^2\\ x-5=9\\ x=14.\)

Đáp án: Khoai lang, sắn, gạo.

\(A=2^2.2^4.2^6...2^{100}\) 

Đặt: \(P=2+4+6+...+100\)

Tổng của \(P\) là:

     \(\left(100-2\right):2+1.\left[\left(100+2\right):2\right]=2550\) 

\(\Rightarrow A=2^{2550}\)