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18 tháng 8 2017

bn ơi hình như sai đề 1+1/99.100 => 1+1/99.101 hihi

19 tháng 8 2017

Uk để mik coi lại đề

22 tháng 2 2021

\(\left(2x+1\right)\cdot\left(y-5\right)=12\)

<=>\(x=\frac{17-y}{2y-10}\)

thay x vào phương trình 

=>\(\left(\frac{17-y+y-5}{y-5}\right)\cdot\left(y-5\right)=12\)

<=>\(\frac{12}{y-5}\cdot\left(y-5\right)=12\)

<=>\(12=12\)(Luôn đúng khi và chỉ khi y khác 5 )\(y\ne5,y\inℝ\)

giả sử thay y=1 ta có 

=>\(2x=\frac{12}{1-5}-1\)

<=>\(2x=-4\)

=>\(x=-2\)

Vậy \(x=-2\)và \(y=1\)

13 tháng 3 2016

MÌNH BIK LÀM CÂU A THUI, mình ko ghi lại đề nha

P=1/2.2/3.3/4........99/100

(Nhân tử với tử, mẫu nhân với mẫu ) ta có 

P=1.2.3.4.......99/2.3.4...........100

P=1/100

13 tháng 3 2016

\(P=\frac{1}{2}.\frac{2}{3}......\frac{99}{100}=\frac{1.2.3....99}{2.3.4....100}=\frac{1}{100}\)

\(Q=\frac{4}{1.3}.\frac{9}{2.4}.....\frac{9901}{99.100}=\frac{2^2}{1.3}.\frac{3^2}{2.4}.....\frac{99^2}{99.100}=\frac{2^2.3^2...99^2}{1.2.3^2....98^2.99.100}=\frac{2.99}{100}=\frac{99}{50}\)

24 tháng 8 2018

B1:

a,\(\left(3x-2\right)\left(x-3\right)=3x^2-9x-2x+6=3x^2-11x+6\)

b,\(\left(2x+1\right)\left(x+3\right)=2x^2+6x+x+3=2x^2+7x+3\)

c,\(\left(x-3\right)\left(3x-1\right)=3x^2-x-9x+3=3x^2-10x+3\)

B2:

1)\(x^2-\left(x+4\right)\left(x-1\right)=x^2-\left(x^2-x+4x-4\right)=x^2-x^2+x-4x+4=-3x+4\)

2)\(x\left(x+2\right)-\left(x-2\right)\left(x+4\right)=x^2+2x-\left(x^2+4x-2x-8\right)\)

\(=x^2+2x-x^2-4x+2x+8=8\)

13 tháng 1 2019

Nếu đề là tìm n để phím chia hết thì làm như sau
 n^2 +3n -7 : n-3
n(n+3)-7: n-3
 vì n(n+3) chia hết cho n+3 nên để n^2 +3n -7 chia hết cho n+3 thì -7 chia hết cho n+3
=> n+3 thuộc Ư(7)={1,7,-1,-7}
n+3=1 => n= -2
n+3=7 => n= 4
n+3 = -1 => n=-4
n+3=7 => n =-10
 

b, n^2 +5 : n+1 
n^2 -1+6 : n+1
(n-1)(n+1) + 6: n+1         ( n^2 -1 =(n+1)(n-1) là dùng hằng đẳng thức lớp 8 sẽ học)
vì (n-1)(n+1) chia hết cho n+1 nên để n^2 +5 chia hết n+1 thì 6 phải chia hết cho n+1
=> n+1 thuộc Ư(6)={1,2,3,6,-1,-2,-3,-6}
n+1 =1 =>n=0
n+1=2=>n=1
n+1=3=>n=2
n+1=6=>n=5
n+1=-1=>n=-2
n+1=-2=>n=-3
n+1=-3=>n=-4
n+1=-6=>n=-7

27 tháng 2 2017

Chào bạn !Mình kết bạn nha!

27 tháng 2 2017
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                               
\(B=\frac{3+1}{3}+\frac{8+1}{8}+...+\frac{2014.2016+1}{2014.2016}+\frac{2015.2017+1}{2015.2017}\)         
\(=\frac{2^2}{3}+\frac{3^2}{8}+....+\frac{2015^2}{2014.2016}+\frac{2016^2}{2015.2017}\)         
=\(\frac{2.2}{3}+\frac{3.3}{2.4}+...+\frac{2015.2015}{2014.2016}+\frac{2016.2016}{2015.2017}\)         
=\(\frac{\left(2.3....2015.2016\right)+\left(2.3.....2015.2016\right)}{\left(1.2.3.....2014.2015\right)+\left(3.4....2016.2017\right)}\)         
=\(2016+\frac{2}{2017}\)         
          
          
          
          
          
          
          
          
          
          
          
                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                      
 
1 tháng 3 2018

help me !! mik cần giải bài này gấp các bn giải nhanh dùm mik đi

12 tháng 3 2018

Anh k biết em ak

18 tháng 8 2023

Tiền lãi của chiếc quạt là:

\(20\%\times1800000=360000\left(đ\right)\)

Giá vốn của chiếc quạt: 

\(1800000-360000=1440000\left(đ\right)\)

Đáp số: ...

18 tháng 8 2023

1440000đ nha