thuc hien phep tinh
a) S1=2+2^2+2^3+...+2^90
b)S2= (-2) +(-2)^2 +(-2)^3+...(-2)^100
c)S3=2^100-2^99-2^98-2^97-...-2^2-2-1
d)S4=1-3+5-7+...+2001-2003+2005-
Thực hiện phép tính :
a, S1=2+2^2+2^3+...+2^90
b, S2=(-2)+(-2)^2+(-2)^3+...+(-2)^100
c, S3=2^100-2^99-2^98-2^97-...-2^2-2-1
d, S4=1-3+5-7+...+2001-2003+2005-2007
a, S1=2+2^2+2^3+...+2^90
=>2S1=2^2+2^3+2^4+...+2^91
=>2S1-S1=(2^2+2^3+2^4+...+2^91)-(2+2^2+2^3+...+2^90)
=>S1=2^91-1
chỉ thằng lười mới khó hiểu ,bài này suy nghĩ một chút thì rất dễ
1) Tim A , biet :
(242 / 363 - 1616 / 2121) = 2 / 7 x A
2)Thuc hien phep tinh :
99 / 98 - 98 / 97 + 1 / 97 x 98
1) Thuc hien phep tinh (nhanh neu co the):
a) 21.(-35)-3.(-25).7
b) 77-11.(30+7)
c) 85.(35-27)-35.(85-27)
d) (-25).68+(-34).(-250)
e) 125.(-61).(-23).(-1)2n+1/ n thuoc N
f) 1-2+3-4+...+49-50+51
g)1-2-3+4+5-6-7+...+97-98-99+100
h) 2100-299-298-...-22-2-1
Làm đc câu nào thì làm nha
a) 21.(-35)-3.(-25).7=21.(-35)-(21.(-25)=21(-35+25)=21.(-10)=-210
b)77-11(30+7)=77-11.7+11.30=77-77-330=-330
c)85(35-27)-35(85-27)=85.35-85.27-35.85+35.27=(85.35-35.85)+(35.27-85.27)=35.27-85.27=27(35-85)=27.(-50)=-1350
d)(-25).68+(-34).(-250)=-25.68+34.2.125=-25.68+68.125=68(125-25)=68.100=6800
e)125.(-61).(-2^3).(-1)^2n+1=125.(-61).(-8).(-1)=(-8.125).61=-1000.61=-61000
h) đặt S=2100-299-298-...-22-2-1=2^100-(2^99+2^98+2^97+...+2+1)=2^100-A
ta có: A=2^99+2^98+2^97+...+2+1
2A=2^100+2^99+2^98+...+2^2+2
=>2A-A=(2^100+2^99+2^98+...+2^2+2)-(2^99+2^98+2^98+...+2+1)
=>A=2^100-1
=>S=2^100-(2^100-1)=2^100-2^100+1=1
A=2^100
a là bằng -210
ý b bằng -330
ý c bằng -1350
ý d bằng 6800
ý f bằng 225
tớ làm được 5 ý , tich nha bạn
a, 21.(-35)-3.(-25).7
=21.(-35)-(3.7).(-25)
=21.(-35)-21.(-25)
=21.[(-35)-(-25)]
=21.(-10)
=-210
thuc hien cac phep tinh
1-2-3+4+5-6-7+...+2001-2002-2003+2004
Tính
S1=1+2^2+2^3+........+2^20
S2=1+3+3^2+.....+3^15
S3=6+5^2+5^3+.....+3^15
S4=1×2+2×3+3×4+....+99×100
S5=2×2+2×5+3×8+.....+50×149
Bài 1:D=1000+998+996+...+2-999-997-995-1
E=100+98+96+94+...+2-97-95-93-...-1
G=1-3+5-7+...+2005-2007+2009
H=1-3+5-7+...+2001-2003+2005
I=1+0-3-4+5+6-7-8+9+...-299+300+301+302
K=1-2+3-4+...+2017-2018+2019
L=1-2-3+4+5-6-7+...+1997+1998-1999+2000+2001
M=1-2+3-4+5-6+...+99-100+101
Bài 2:A=1+2+3+...+x
B=2+4+6+...+2.x
C=1+3+5+7+...+(2x-1)
Tính tổng : a) S2 = 1 - 3 + 5 - 7 + 9 - 11 + ... + 2005 - 2007. b) S3 = 1 + 2 + 3 - 4 - 5 - 6 + 7 + 8 + 9 - 10 - 11 - 12 + ... + 97 + 98 + 99 - 100 - 101 - 102
Cho S1=1+2, S2=2+3+4, S3=3+4+5+6, S4=4+5+6+7+8............ tinh S100
Tính
a, A= 1-3+5-7+.......+2001-2003+2005
b,B=1-2-3+4+5-6-7+8+.........+1993-1994
c,C=1+2-3-4+5+6-7-8+9+......+2002-2003-2004+2005+2006
d,D=12-22+32-42+......+992-1002+1012
Mời bạn tham khảo các link sau:
a),b),c):https://hoidap247.com/cau-hoi/214111
d):https://olm.vn/hoi-dap/detail/78449788871.html
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