1382 -382 = (138 - 38)(138+38) = 100.176 = 17600
1382 -382 = (138 - 38)(138+38) = 100.176 = 17600
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
so sánh 2 số avàb biết
a=6+5^2+5^3+.....+5^1997+5^1998
b=(5^999*(5^1000+2)-10*5^998-1)/4
Tính nhanh:
a) 642 + 382 + 128 . 36 ; b) 76 . 56 - (353 + 2) . (353 - 2) ; c) 19972 - 1996 . 1998
Baif2:
Tìm số dư khi :
a) 2^1994 cho 7
b) 3^1998 +5^1998 cho 13
c) A=1^3 +2^3 +...+99^3 chia cho B =1+2+3+...+99
Tính nhanh (10^2+8^2+6^2+4^2+2^2)-(9^2+7^2+5^2+3^2+1^2)
Tính nhanh 1998^2-1997(1998+1)
Tính A = -1^2 -2^2 - 3^2 + 4^2 -5^2 -6^2 - 7^2 +8^2 -...-99^2 +100^2?
Tính A = -1^2 -2^2 - 3^2 + 4^2 -5^2 -6^2 - 7^2 +8^2 -...-99^2 +100^2?
862 - 142=?
19982 - 1997. (1998+1)=?