(x+1)+(x+2)+(x+3)+.....+(x+99) = 9900

x+x+x+....+x+(1+2+3+...+99) = 9900

50x + 2500 = 9900

=> 50x =7400

=> x = 148

sao số số hạng lại ra là 50 số vậy

trung hiếu làm sai rồi phải làm như này :(x+x+x.......+x)+(1+2+3+....+99)=9900

=99*x+4950=9900

=99*x=4950

x=50

(x+1)+(x+2)+...+(x+98)+(x+99)=9900

x.99+(1+2+3+...+98+99)=9900

x.99+[(99-1):1+1].(99+1):2=9900

x.99+99.100:2

x.99+99.50=9900

x.99+4950=9900

x.99=9900-4950

x.99=4950

x=4950:99

x=50

chúc bạn học tốt nha

\(\left(x+1\right)+\left(x+2\right)+...+\left(x+98\right)+\left(x+99\right)=9900\)

\(\left(x+x+x+...+x+x\right)+\left(1+2+3+...+99\right)=9900\)

  \(\left(99\cdot x\right)+\left(100\times99\div2\right)=9900\)

\(99x+4950=9900\)

\(99x=9900-4950\)

\(x=4950\div99\)

\(x=50\)

=> :(x+x+x+...+x)(co 99so hang)+(1+2+3+...+99)=9900

 => :x.99+(99+1).99:2=4950=9900

=>:x.99+4950=9900

=>:x.99=9900-4950=4950

=>x=4950:90=55

vay x=55

(x+1)+(x+2)+...+(x+98)+(x+99)=9900

x+x+x+x+...x+(1+2+...+98+99)=9900

50x+2500=9900

=>50x=7400

vậy x=148

\(\Rightarrow99x+\left(1+2+3+...+98+99\right)=9900\)(vì có 99 số hạng nha)

\(\Rightarrow99x+4950=9900\)

\(\Rightarrow99x=4950\)

\(\Rightarrow x=50\)

( x + 1 ) + ( x + 2 ) + ... + ( x + 98 ) + ( x + 99 ) = 9900

( x + x + ... + x + x ) + ( 1 + 2 + ... + 98 + 99 ) = 9900

99.x + \(\frac{\left(99+1\right).99}{2}\)= 9900

99.x + 4950 = 9900

99.x = 9900 - 4950

99.x = 4950

x = 4950 : 99

x = 50

2 . x + 5 . x - 3 . x = 125 : 4 + 27 : 3

x . ( 2 + 5 - 3 ) = 31,25 + 9

x . 4 = 40,25

x = 40,25 : 4

x = 10,0625

phan thuhai???

\(\left(x+1\right)+\left(x+2\right)+...+\left(x+99\right)=9900\)

\(\Leftrightarrow99x+\left(\frac{99-1}{1}+1\right)=9900\)

\(\Leftrightarrow99x=9900-99\)

\(\Leftrightarrow x=99\)

k mk nha

(x + 1) +( x + 2) + ... + (x + 99 )= 9900

=>99x +(99-1/1  + 1 )=9900

=>99x=9900-99

=>x=90

ấn chậm quá

@@

làm lại nha . làm theo này chăc chắn hơn

(x+1)+(x+2)+...+(x+98)+(x+99)=9900

=>99x + ( 1+2+3+...+99)=9900

=>99x + 4950 = 9900

=> 99x = 4950

=> x= 50

vậy ...

Chắc chắn #

Đưa về: x. (1/1-1/2+1/2-1/3+...-1/99+1/99-1/100) = 99

=> 99x/100 = 99

=> x = 100

Ta có : 

\(\frac{x+1}{100}+\frac{x+2}{99}=\frac{x+3}{98}+\frac{x+4}{97}\)

\(\Leftrightarrow\)\(\left(\frac{x+1}{100}+1\right)+\left(\frac{x+2}{99}+1\right)=\left(\frac{x+3}{98}+1\right)+\left(\frac{x+4}{97}+1\right)\)

\(\Leftrightarrow\)\(\frac{x+101}{100}+\frac{x+101}{99}=\frac{x+101}{98}+\frac{x+101}{97}\)

\(\Leftrightarrow\)\(\frac{x+101}{100}+\frac{x+101}{99}-\frac{x+101}{98}-\frac{x+101}{97}=0\)

\(\Leftrightarrow\)\(\left(x+101\right)\left(\frac{1}{100}+\frac{1}{99}-\frac{1}{98}-\frac{1}{97}\right)=0\)

Vì \(\frac{1}{100}+\frac{1}{99}-\frac{1}{98}-\frac{1}{97}\ne0\)

Nên \(x+101=0\)

\(\Rightarrow\)\(x=-101\)

Vậy \(x=-101\)

Chúc bạn học tốt ~ 

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