Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Dựng hình bình hành ABCD.
Khi đó vì M là trung điểm AC nên M cũng là trung điểm BD \(\Rightarrow\) M, B, D thẳng hàng.
Lại có ABCD là hình bình hành \(\Rightarrow AD=BC\)
Mà \(AK=BC\) nên \(AK=AD\)
\(\Rightarrow\Delta ADK\) cân tại A
\(\Rightarrow\widehat{AKD}=\widehat{ADK}\) hay \(\widehat{LKB}=\widehat{KDA}\)
Mặt khác, LB//AD nên \(\widehat{KDA}=\widehat{KBL}\) (2 góc đồng vị)
Do đó \(\widehat{LKB}=\widehat{KBL}\left(=\widehat{KDA}\right)\)
\(\Rightarrow\Delta KBL\) cân tại L
\(\Rightarrow LK=BL\) (đpcm)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=x^3-5x^2+3x+9\\ =x^3+x^2-6x^2-6x+9x+9\\ =x^2\left(x+1\right)-6x\left(x+1\right)+9\left(x+1\right)\\ =\left(x^2-6x+9\right)\left(x+1\right)\\ =\left(x-3\right)^2\left(x+1\right)\)
A = \(x^3\) - 5\(x^2\) + 3\(x\) + 9
A = \(x^3\) - 3\(x^2\) - \(x^2\) - \(x^2\) + 3\(x\) + 9
A = (\(x^3\) - 3\(x^2\)) - (\(x^2\) - 3\(x\)) - (\(x^2\) - 9)
A = \(x^2\)(\(x\) - 3) - \(x\)(\(x\) - 3) - (\(x\) - 3)(\(x\) + 3)
A = (\(x\) - 3)(\(x^2\) - \(x\) - \(x\) - 3)
A = (\(x\) - 3)[\(x^2\) - (\(x+x\)) - 3]
A = (\(x\) - 3)[\(x^2\) - 2\(x\) - 3]
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2x^2-3x+1\\ =2x^2-x-2x+1\\ =\left(2x^2-x\right)-\left(2x-1\right)\\ =x\left(2x-1\right)-\left(2x-1\right)\\ =\left(2x-1\right)\left(x-1\right)\)
\(2x^2-3x+1\\ =2x^2-2x-x+1\\ =2x\left(x-1\right)-\left(x-1\right)\\ =\left(2x-1\right)\left(x-1\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\left(4x^2-2x-1\right)-\left(x^2-4x+2\right)\\ =4x^2-2x-1-x^2+4x-2\\ =3x^2+2x-3\)
Thay `x=-1/2` vào A ta có:
\(A=3\cdot\left(-\dfrac{1}{2}\right)^2+2\cdot-\dfrac{1}{2}-3=\dfrac{3}{8}-1-3=\dfrac{3}{8}-4=-\dfrac{29}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
You know, we have many kinds of game that we can play them anytime.But in my class, we find chess the most exciting.Because it improve our brain.
a; \(x^2\) - 6\(x\) + 8
= \(x^2\) - 2\(x\) - 4\(x\) + 8
= (\(x^2\) - 2\(x\)) - (4\(x\) - 8)
= \(x\)(\(x\) - 2) - 4(\(x\) - 2)
= (\(x-2\))(\(x\) - 4)
4\(x^2\) + 4\(x\) - 3
= 4\(x^2\) - 2\(x\) + 6\(x\) - 3
= (4\(x^2\) - 2\(x\)) + (6\(x\) - 3)
= 2\(x\)(2\(x\) - 1) + 3(2\(x\) - 1)
= (2\(x\) - 1)(2\(x\) + 3)