Unless they knew you, they wouldn't give you some precious information. 

-> Trong câu này If...not = Unless nhé.

a) Dựng ảnh ↓

b) đặc điểm của ảnh : Ảnh thật, ngược chiều và nhỏ hơn vật

c)

\(tacó\Delta OAB\) ~\(\Delta O\char"0391 \text{`B`}\)

=> \(\frac{OA`}{OA}\) =\(\frac{A`B`}{AB}\) (1)

\(\Delta=FAB\) ~\(\Delta FOI\)

=>\(\frac{OF}{OA`-OF}=\frac{OI}{AB}\) (2)

Từ (1) và (2), ta có:

\(\frac{1}{OA}+\frac{1}{OA`}=\frac{1}{OF}\)

<=>\(\frac{1}{30}+\frac{1}{OA`}=\frac15\)

=> OA' = 6 cm

\(\Rightarrow A`B`=\frac{OA`}{OA}\times AB=\frac{6}{30}\times5=1\) cm

Vậy khoảng cách từ quang tâm O đến ảnh là 6 cm

chiều cao của ảnh là 1 cm

a: Xét tứ giác BCEF có \(\widehat{BFC}=\widehat{BEC}=90^0\)

nên BCEF là tứ giác nội tiếp

Transistor gồm ba lớp bán dẫn ghép với nhau hình thành hai mỗi tiếp giáp P- N, nếu ghép theo thứ tự PNP ta được transistor thuận, nếu ghép theo thứ tự NPN ta được transistor ngược. Về cấu tạo, transistor tương đương với hai diode đấu ngược chiều nhau.

@An Lâm, Bạn ghi tham khảo vào bạn neh!

ĐKXĐ: \(x\ge2\)

\(\sqrt{4x-8}-\sqrt{x-2}=2\)

\(\Leftrightarrow\sqrt{4\left(x-2\right)}-\sqrt{x-2}=2\)

\(\Leftrightarrow2\sqrt{x-2}-\sqrt{x-2}=2\)

\(\Leftrightarrow\sqrt{x-2}=2\)

\(\Leftrightarrow x-2=4\)

\(\Leftrightarrow x=6\) (thỏa mãn)

Tham khảo nha:

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