1+2+3+...+99+100
=(1+100)x50
=101x50
=5050
1+2+3+...+99+100
s=100+99+...+2+1
nen 2s=101+101+...+101+101 (co100so hang)
s=101*100/2=5050
Tính : C=101+100+99+98+...+3+2+1 phần101-100+99-98+...+3-2+1
Tính nhanh
a) 1 + 2 + 3 + … + 99 + 100 b) 2 + 4 + 6 + … + 96 + 98
c) (–1) + 2 + (–3) + 4 + … + (–99) +100 d) –1 + 2 – 3 + 4 – … – 99 + 100
Tính
1) S=1-2+3-4+......+99-100
2) P=2-4+6-8+........+98-100
3) Q=(-1)+2+(-3)+.......+(-99)+100
tính tổng
1-2+3-4+....+99-100
-1+3-5+7-....-97+99
1+2-3-4+...+97+98-99-100
Bài 4: Tính tổng 1) 1 + (-2) + 3 + (-4) + . . . + 19 + (-20) 2) 1 – 2 + 3 – 4 + . . . + 99 – 100 3) 2 – 4 + 6 – 8 + . . . + 48 – 50 4) – 1 + 3 – 5 + 7 - . . . . + 97 – 99 5) 1 + 2 – 3 – 4 + ... + 97 + 98 – 99 - 100
1,tính :
a, 1+2+3+4+5+........+99+100
b, 1+( -2 )+3+( -4)+5 +.........+99+( -100)
Tính: (100-1^2)(100-2^2)(100-3^3)...(100-99^2)
Tính
A=1*2+2*3+3*4+..+99*100
B=1*3+3*5+5*7+..+97*99
C=1*2*3+2*3*4+...+98*99*100
Tính tổng 100-(1+1/2+1/3+1/4+...+1/100)/1/2+2/3+3/4+....+99/100
Câu 13: Tính: \(1+2^2+3^3+...+99^{99}+100^{100}\)
