Question

a)(864x11-423x4):(432x(3+6+9+...+27-132))

b)1x2+2x3+3x4+...+99x100

c)\(\frac{1+\left(1+2\right)+\left(1+2+3\right)+\left(1+2+3+4\right)+...+\left(1+2+3+...+99\right)}{1x9+2x98+3x97\: +....+99x1}\)

giúp mk với , mk tick cho , nha !!!!

Answer 1

tính nhanh nha

Answer 2

Mình chỉ tính câu b và c thội nhé!.

Ta có:

b) \(1.2+2.3+3.4+...+99.100\)

\(=\frac{99.100.101}{3}=333300\)

c) \(\frac{1+\left(1+2\right)+\left(1+2+3\right)+...+\left(1+2+3+...+99\right)}{1.99+2.98+3.97+...+99.1}\)

\(=\frac{1+1+2+1+2+3+1+2+3+4+...+1+2+3+...+99}{1.99+2.98+3.97+...+99.1}\)

\(=\frac{\left(1+1+...+1\right)+\left(2+2+...+2\right)+\left(3+3+...+3\right)+....+99}{1.99+2.98+3.97+...+99.1}\)

\(=\frac{1.99+2.98+3.97+...+99.1}{1.99+2.98+3.97+...+99.1}=1\)