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Phần A hình như sai đầu bài , mình sửa lại và làm luôn nhé :
A = ( 2 + 4 + 6 + 8 .... + 100 ) x ( 142142 x 143 - 143143 x 142 )
A = ( 2 + 4 + 6 + 8 + ... + 100 ) x ( 142 x 1001 x 143 - 143 x 1001 x 142 )
A = ( 2 + 4 + 6 + 8 + .. + 100 ) x 0
A = 0
B = ( 630 - 315 x 2 ) : ( 1 + 2 + 3 + ... + 1000 )
B = ( 630 - 630 ) : ( 1 + 2 + 3 + ... + 100 )
B = 0 : ( 1 + 2 + 3 + ... + 100 )
B = 0
5050 + X x 15 = 1000
=> X x 15 = -4050
Vậy x=-4050 : 15 = -270
1=ĐS=1
2=ĐS=2000
3=ĐS=0
4=ĐS=7036
K MÌNH NHA
= 1/1x2 + 1/2x3 + 1/3x4 ...... +1/9x10
= 1-1/2+1/2-1/3+1/3-1/4+........+1/9-1/10
=1-1/10=9/10
đặt A=1/1 x 1/2 + 1/2 x 1/3 + 1/3 + 1/4 + .......... + 1/9 x 1/10
\(A=\frac{1}{1}\cdot\frac{1}{2}+\frac{1}{2}\cdot\frac{1}{3}+...+\frac{1}{9}\cdot\frac{1}{10}\)
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}\)
\(=\frac{9}{10}\)
đặt B=2/1 x 2 + 2/2 x 3 + 2/3 x4 + .............. + 2/98 x 99 + 2/99 x 100
\(B=2\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\right)\)
\(=2\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=2\left(1-\frac{1}{100}\right)\)
\(=2\times\frac{99}{100}\)
\(=\frac{99}{50}\)
a, X:6x4=1,248 =>X=1,248:4x6=1,872
b,7xX-2xX=1,85 =>5xX=1,85 =>X=1,85:5=0,37
c,Xx1000=499,7 =>X=499,7:1000=0,4997
d, 100xX=273,5 =>X=273,5:100=2,735
what abou you ?
how are you ?
what you name ?
how maney bananas
A. \(\left(x+1\right)+\left(x+2\right)+......+\left(x+100\right)=5750\)
\(x+1+x+2+....+x+100=5750\)
\(100x+\left(1+2+3+.......+100\right)=5750\)
\(100x+5050=5750\)
\(100x=700\)
\(x=700:100=7\)
B. x+(1+2+......+100) = 2000
x + 5050 = 2000
x = 2000 - 5050
x= -3050
C. ( x-1 )+(x-2)+......+( x - 100 ) = 50
x-1+x-2+.........+x-100 = 50
100x + ( -1-2-........-100 ) = 50
100x + ( - 5050 ) = 50
100x = 50 + 5050
100 x = 5100
x = 5100 : 100
x = 51
A . \(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+100\right)=5750\)
\(\left(x+x+x+...+x\right)+\left(1+2+3+...+100\right)=5750\)
\(100x+5050=5750\)
\(100x=5750-5050\)
\(100x=700\)
\(\Rightarrow x=\frac{700}{100}=7\)
B. \(x+\left(1+2+3+4+5+....+100\right)=2000\)
\(x+\frac{\left(100+1\right).100}{2}=2000\)
\(x+5050=2000\)
\(\Rightarrow x=2000-5050=-3050\)
C. \(\left(x-1\right)+\left(x-2\right)+\left(x-3\right)+....+\left(x-100\right)=50\)
\(\left(x+x+x+...+x\right)-\left(1+2+3+...+100\right)=50\)
\(100x-5050=50\)
\(100x=5100\)
\(\Rightarrow x=\frac{5100}{100}=51\)
giúp mik nhé cám ơn
=28