Question

[Phan Tiến Dũng]

Tìm x, biết:

1) 1/3. x + 2/5. (x - 1) = 0

2) (2 x - 3).(6 - 2 x) =0

3) (3 x -1).(-1/2 x + 5) = 0

4) (2 x + 3/5)²  - 9/25 = 0

Tính:

1) 4/2.4 + 4/4.6 + 4/6.8 + ... + 4/2008.2010

2) 1/18 + 1/54 + 1/108 + ... +1/990

Answer 1

[︻̷̿┻̿═━დდDarknightდდ]

\(a,\frac{1}{3}x+\frac{2}{5}x-\frac{2}{5}=0\)

\(\frac{11}{15}x=\frac{2}{5}\)

\(x=\frac{6}{11}\)

Answer 2

[︻̷̿┻̿═━დდDarknightდდ]

b,\(\left(2x-3\right).\left(6-2x\right)=0\)

\(\Rightarrow\orbr{\begin{cases}2x-3=0\\6-2x=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{3}{2}\\x=3\end{cases}}\)

Vậy