tính

2/3+2/15+2/35+2/63+2/99

1/1×2+1/2×3+1/3×4+........+1/1995×1996+1/1996×1997

1,Tính nhanh a,16×23+35×34+4×108+7×30 b,198×1996+1997×11+1985 ———————————— 1997 × 1996 - 1995 × 1996 c,1/2+2/8+3/28+4/77+5/176

Rút gọn P/S:

a) -315/540

b) 25*13 / 26*35

c) 6*9-2*17  /  63*3-119

d) 3*13-13*18  /  15*40-80

e) (-5)^3  *  40  *  4^3  /  135  *  (-2)^14  *  (-100)^0  

f) 2929-101/2*1919+404

g) -1997*1996+1/(-1995)*(-1997)+1996

h) 2*3+4*6+14*21/3*5+6*10+21*35

i) 3*7*13*37*39-10101/505050-70707

\(\frac{1}{2}\times\frac{1}{3}\times\frac{1}{4}\times...\times\frac{1995}{1996}\times\frac{1996}{1997}\)

a) A=1-2-3+4+5-6-7+.....+1996+1997-1998-1999+2000

b) B=1-3+5-7+....+2001-2003+2005

c) C=1-2-3+4+5-6-7+8+.....+1993-1994-1995+1996+1997

d) D=1000+998+996+......+10-999-997-995-...-11

a,x-10/1994+x-8/1996+x-6/1998+x-4/2000+x-2/2002=x-2002/2+x-2000/4+x-1998/6+x-1996/8+x-1994/10

b,x-1991/9+x-1993/7+x-1995/5+x-1997/3+x-1999/1=x-9/1991+x-7/1993+x-5/1995+x-3/1997+x-1/1999

c,x-1/13-2x-13/15=3x-15/27-4x-27/29

M= 1-2-3+4+5-6-7+8+...........+1993-1994-1995+1996+1997.

\(\dfrac{x+1}{1998}\)+ \(\dfrac{x+2}{1997}\)=\(\dfrac{x+3}{1996}\)+\(\dfrac{x+4}{1995}\)

Tính nhanh

B = 1996³ - 1 / 1996² + 1997
C = 1995³ + 1 / 1995² - 1994
D = (2² + 4² +...+100²) - (1² + 3² +...+ 99²)
E = 3⁸ . 7⁸ - (21⁴ - 1) (21⁴ +1 )