\(1+1=,,?????\)giup mik nha cac ban
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1
SX
3
15 tháng 10 2016
3S=1x2x3+2x3x3+...+39x40x3
3S=1x2x(3-0)+2x3x(4-1)+...+39x40x(41-38)
3S=1x2x4-1x2x0+2x3x4-2x3x1+.....+39x40x41-38x39x40
3S=39x40x41
S=39x40x41:3
S=13x40x41
S=21320
15 tháng 10 2016
S = 1 x 2 + 2 x 3 + 3 x 4 + ... + 39 x 40
S = 2 + 6 + 12 + ... + 1560
Sau đó tự làm nhé !
28 tháng 6 2017
a) \(\left(x-\dfrac{1}{2}\right)^2=0\)
\(\Rightarrow x-\dfrac{1}{2}=0\)
\(\Rightarrow x=\dfrac{1}{2}\)
b) \(\left(x-2\right)^2=1\)
\(\Rightarrow x-2=1\)
\(\Rightarrow x=3\)
c) \(\left(2x-1\right)^3=-8\)
\(\Rightarrow\left(2x-1\right)^3=\left(-2\right)^3\)
\(\Rightarrow2x-1=-2\)
\(\Rightarrow2x=-1\)
\(\Rightarrow x=\dfrac{-1}{2}\)
d) \(\left(x+\dfrac{1}{2}\right)^2=\dfrac{1}{16}\)
\(\Rightarrow\left(x+\dfrac{1}{2}\right)^2=\left(\dfrac{1}{4}\right)^2\)
\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{1}{4}\\x+\dfrac{1}{2}=-\dfrac{1}{4}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-1}{4}\\x=\dfrac{-3}{4}\end{matrix}\right.\).
28 tháng 6 2017
a , \(\left(x-\dfrac{1}{2}\right)^2=0\)
<=> \(x-\dfrac{1}{2}=0\Rightarrow x=\dfrac{1}{2}\)
b , \(\left(x-2\right)^2=1\Rightarrow\left[{}\begin{matrix}x-2=1\\x-2=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=1\end{matrix}\right.\)
c , \(\left(2x-1\right)^3=-8\Rightarrow2x-1=-2\Rightarrow x=\dfrac{-1}{2}\)
d , \(\left(x+\dfrac{1}{2}\right)^2=\dfrac{1}{16}\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2=\dfrac{1}{4^2}\)
<=> \(\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{1}{4}\\x+\dfrac{1}{2}=\dfrac{-1}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{4}\\x=\dfrac{-3}{4}\end{matrix}\right.\)
16 tháng 11 2019
Ta có : \(\left(3x-1\right)^2-\left(x+7\right)^2=0\)
\(\left(3x-1+x+7\right)\left(3x-1-x-7\right)=0\)
\(\left(4x+6\right)\left(2x-8\right)=0\)
Nên : 4x + 6 = 0 hoặc 2x - 8 = 0
4x = -6 hoặc 2x = 8
x = \(\frac{-3}{2}\) hoặc x = 4
Vậy x = \(\frac{-3}{2}\) hoặc x = 4
10 tháng 12 2018
My name is ....... and I’m a Vietnamese. I am ......... years old. I live in Ho Chi Minh city in the south of Vietnam.
I have a big family with four people. I have one sister and one brother. My sister is older and my brother is younger than me. My father is a teacher at a secondary school. He has worked for 35 years in the field and he is my biggest role model in life. My mother is a teacher too. She is very beautyful and she is really good at cooking. I love my family so much.
(I’m a generous and easy-going person but when it comes to work I’m a competitive perfectionist. I’m also an optimis and outgoing person so I have many friends and other social relationships. I enjoy reading, writing and doing math. I decided to become a Civil Engineer because I have always been fascinated by bridges, buildings, and skyscrapers. A degree in Civil Engineering enables me to achieve my goals and also gives me an opportunity to make a difference in the community.
Five years from now, I want to become a project manager of a construction project. As a project manager, my primary goals are managing people, set budgets, and making decisions of all kinds. I also want to speak English fluently so I can work with people from different countries.)
TC
10 tháng 12 2018
Bài tham khảo:
Hello everyone, my name is Le Ngoc Diep. This year I am 12 years old, I live in Dong Da, Hanoi. There are four members in my family, including my parents, elder brother and me. Now, I am studying in class 9B at Chu Van An school. At school I have a lot of friends, they are all docile and lovely. Everyone says that I am a very active and energe child so they love me so much. My favorite subject is Physics and English. My hobbies are cooking and reading books. Some of the favorite books are science fiction, detective, history and art. In my spare time, I also take an online piano course. In the future, I will try to get more experience to pursue the dream of becoming a famous pianist performing in the world.
4 tháng 1 2017
Vị trí : hang Thẩm Khuyên , Thẩm Hai (Lạng Sơn) ; Núi Đọ (Thanh Hóa); ..............................
1 + 1 = 2
nha ban
1 + 1 = 2 nhé!