a, Trường có:
\(279:31\%=900\left(HS\right)\)
b, Số HS K4 chiếm:
\(270:900\times100\%=30\%\)
ĐS: a)....... ;b).......

\(\#PeaGea\)

    \(30-2\left(3x-1\right)^2=30-12\)
\(\Leftrightarrow2\left(3x-1\right)^2=30-\left(30-12\right)=12\)
\(\Leftrightarrow\left(3x-1\right)^2=12:2=6\)
\(\Leftrightarrow\sqrt{\left(3x-1\right)^2}=\sqrt{6}\)
TH1:
\(\Leftrightarrow3x-1=\sqrt{6}\)
\(\Leftrightarrow3x=\sqrt{6}+1\)
\(\Leftrightarrow x=\dfrac{\sqrt{6}+1}{3}\)
TH2:
\(\Leftrightarrow3x-1=-\sqrt{6}\)
\(\Leftrightarrow3x=\left(-\sqrt{6}\right)+1\)
\(\Leftrightarrow x=\dfrac{\left(-\sqrt{6}\right)+1}{3}\)
Vậy \(x\in\left\{\dfrac{\sqrt{6}+1}{3};\dfrac{\left(-\sqrt{6}+1\right)}{3}\right\}\)


(đề cứ sai sai kiểu gì í)

\(\#PeaGea\)

a) Điểm C nằm giữa hai điểm còn lại
b) Đổi 1,5km = 1500m
Nếu Trạm xăng dầu nằm chính giữa nhà Tùng và Trường học ⇒ \(ND=DT=1500:2=750\left(m\right)\)
Khoảng cách từ Trạm xăng dầu đến Của hàng sách là: \(750-300=450\left(m\right)\)
Vậy: a)................
      : b)................

\(\#PeaGea\)

Khó.

Đổi: 800dm = 80m
Diện tích mảnh đất HCN là:
\(55\times80=4400\left(m^2\right)\)
Ta có sơ đồ:

DT trồng nhãn là:
\(\left(4400-800\right):2=1800\left(m^2\right)\)
DT trồng vải là:
\(1800+800=2600\left(m^2\right)\)
Đ/S: .......

\(\#PeaGea\)

Break a leg có nghĩa là: Chúc may mắn (?)

a)  \(\dfrac{-3}{5}+\dfrac{7}{21}+\dfrac{-4}{5}+\dfrac{7}{5}\)
\(=\left(\dfrac{-3}{5}+\dfrac{-4}{5}+\dfrac{7}{5}\right)+\dfrac{1}{3}\)
\(=0+\dfrac{1}{3}=\dfrac{1}{3}\)

b)  \(\left(\dfrac{1}{4}+\dfrac{-5}{13}\right)-\left(\dfrac{8}{13}-\dfrac{2}{11}\right)-\dfrac{3}{-4}\)
\(=\dfrac{1}{4}+\dfrac{-5}{13}-\dfrac{8}{13}+\dfrac{2}{11}-\dfrac{-3}{4}\)
\(=\left(\dfrac{1}{4}-\dfrac{-3}{4}\right)+\left(\dfrac{-5}{13}-\dfrac{8}{13}\right)+\dfrac{2}{11}\)
\(=1+\left(-1\right)+\dfrac{2}{11}\)
\(=0+\dfrac{2}{11}=\dfrac{2}{11}\)

c)  \(\dfrac{11}{15}\cdot\dfrac{4}{7}+1\dfrac{3}{7}\cdot\dfrac{11}{15}-\dfrac{11}{15}\)
\(=\dfrac{11}{15}\left(\dfrac{4}{7}+\dfrac{10}{7}-1\right)\)
\(=\dfrac{11}{15}\cdot1=\dfrac{11}{15}\)

\(\#PeaGea\)

Rewrite the sentences with the same meaning.
35. I have a red dress, and she has a blue one.
A. The red dress is mine, and the blue one is hers.
B. A red dress is mine, and a blue one is hers.
C. A red dress is mine, and a blue one is her.
D. A red dress is my, and a blue one is she.

mọi người ghi cả lí do nhé