=1*100+2*(100-1)+3*(100-2)+.....+100*(100-99)
=100*(1+2+3+....+100)-(1*2+2*3+...+99*100)
=100*101*100/2-99*100*101/3=171700
k mk nha
=1*100+2*(100-1)+3*(100-2)+.....+100*(100-99)
=100*(1+2+3+....+100)-(1*2+2*3+...+99*100)
=100*101*100/2-99*100*101/3=171700
k mk nha
Tính : \(B=\dfrac{1}{1.100}+\dfrac{1}{2.99}+\dfrac{1}{3.98}+\dfrac{1}{4.97}+...+\dfrac{1}{50.51}\)
Tính nhanh 1.100+2.99+3.98+...+99.2+100.1
F=1.100+2.99+3.98+...+99.2+100.1
tính tổng
T = 1.100+ 2.99 + 3.98+ ....+ 99.2 + 100.1
Tính nhanh F = 1.100 + 2.99 + 3.98 + ... + 98.3 + 99.2 + 100.1
Tính tổng:
F = 1.100 + 2.99 + 3.98 +...+ 98.3 + 99.2 + 100.1
Tính nhanh
A)A=1.2+2.3+3.4+....+98.3+99.2+100.1
B)B=1.100+2.99+3.98+...+98.3+99.2+100.1
a, A1 = 10.11+11.12+12.13+.......+29.30
b, A2 = 10.12+11.13+12.14+......+200.202
c, A3 = 1.100+2.99+3.98+4.97+.......+100.1
d, A4 = 4+12+24+40+.......+19404
e, A5 = 6+16+30+48+......+19600
Tính nhanh 1.100+2.99+3.98+...+98.3+99.2+100.1/1.2+2.3+3.4+...+99.100