1/3x4 + 1/4x5 + 1/5x6 +...+ 1/97x 98 + 1/98x99 + x =1
=> 1/3-1/4+1/4-1/5+1/5-1/6+....+1/97-1/98 + 1/98-1/99 +x = 1
=> 1/3 - 1/99 +x=1
=> 32/99+x=1
=> x= 1-32/99
=> x = 67/99
1/3x4+1/4x5+1/5x6+...+1/11x12=x?
(x+1/2x3)+(X+1/3x4)+(X+1/4x5)+(X+1/5x6)=25/3
1/3x4 + 1/4x5 + 1/5x6 + ... + 1/20x21 = x/14
Tính : 1/4x5 + 1/5x6 + ................. + 1/98x99 + 1/99x100
Tìm x
a) ( x - 25 ) : 15 = 20
b) 3 x x - 25 = 80
Tính nhanh tổng sau
S= 1/2x3 + 1/3x4 + 1/4x5 + .... + 1/98x99 + 1/99x100
Bạn nào làm nhanh , mk sẽ tk cho
\(\frac{1}{2x3}x\frac{1}{3x4}x\frac{1}{4x5}x............x\frac{1}{98x99}x\frac{1}{99x100}\)
Hãy tính nhanh ,ai nhanh mình tick cho
Cho A=1/2x3+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+.....+1/98x99
Chứng minh rằng 1/5<A<2/5
1/2x3+1/3x4+1/4x5+1/5x6=.......1/99x100
1/2x3 + 1/3x4 + 1/4x5 + 1/5x6 + ....... + 1/19x20. giup mik ik ah. thank
