\(E=1.2+2.3+3.4+...+99.100\)
\(3E=1.2.3+2.3.\left(4-1\right)+...+99.100.\left(101-98\right)\)
\(3E=1.2.3+2.3.4-1.2.3+...+99.100.101-98.99.100\)
\(3E=99.100.101\)
\(E=\dfrac{99.100.101}{3}\)
\(E=333300\)
tìm x ∈ Z
a)1+2+3+.....+x=5050
b)1/2+1/6+.......+1/x2+x=99/100
c)1/6+1/12+........+1/x2-x=59/100
d)x-2017+x-2016+.......+99+100=0
e)x-1+x-2+x-3+.........+x-2017=0
1*2+2*3+3*4+4*5+.........+99*100 = ?
Tính :
a)
A= 1-2+3-4+5-6+...+99-100
b)
B= (10-1).(10-2).(10-3)....(10-99).(10-100)
C = 1-2+3-4+...+99-100+101
A=\(\dfrac{1}{3}\)-\(\dfrac{2}{3^2}\)+\(\dfrac{3}{3^3}\)-\(\dfrac{4}{3^4}\)+...+\(\dfrac{99}{3^{99}}\)-\(\dfrac{100}{3^{100}}\).Chứng minh rằng: A <\(\dfrac{3}{16}\)
1- 2 - 3 + 4 + 5 + 6 + 7 + 8 + . . . + 97 - 98 -99 +100
Tính :
\(A=\dfrac{101+100+99+98+...+3+2+1}{101-100+99-98+...+3-2+1}\)
Tính tổng sau bằng cách hợp lý
A = 5+52+53+...+5100
C = 1-2+3-4+...+99-100+101
Tính A
A = 1 + (-2) + (-3) + 4 + 5 + (-6) + (-7) + 8 + ... + 99 - 100 - 101 + 102 +103