600 + 400 = 1000 nha bạn

\(\frac{1}{5}+\frac{2}{5}+\frac{3}{5}+\frac{4}{5}=\frac{1+2+3+4}{5}=\frac{10}{5}=2\)

1000 nha , mk nhanh nhất

600+400=1000 k mk mk k lại!!!!

\(-x+20=15+8\Rightarrow-x+20=23\Rightarrow-x=23-20\)

\(\Rightarrow-x=3\Rightarrow x=-3\)

20+20=40

40 nha bạn

20+20=40

20+20=40

\(A=4+4^2+4^3+...+4^{100}\)

\(A=\left(4+\text{ }4^2\right)+\left(4^3+4^4\right)+...+\left(4^{99}+4^{100}\right)\)

\(A=\left(1+4\right).\left(4\right)+\left(1+4\right).\left(4^3\right)+...+\left(1+4\right).\left(4^{99}\right)\)

\(A=5.\left(4+4^3+4^5+...+4^{99}\right)\)

Vậy A chia hết cho 5

Các bạn nha!