Tìm x: a, $\frac{x-7}{2020}$ + $\frac{x-7}{2021}$ = $\frac{x-7}{2020}$ b, $\frac{1}{2}$x – $\frac{1}{6}$x + 1 = 0

Đáp án:

`a)`

` (x-7)/2020 + (x-7)/2021 = (x-7)/2020`

` => (x-7)/2020 + (x-7)/2021 –  (x-7)/2020=0`

` => (x-7)(1/2020 + 1/2021 – 1/2020) = 0`

` => (x-7). 1/2021 = 0`

` => x – 7 = 0`

` => x= 7`

Vậy `  x = 7`

` b)`

` 1/(2)x – 1/(5)x +1  = 0`

` => x (1/2 – 1/5) +1 = 0`

` => 3/(10)x + 1 = 0`

` => 3/(10)x = -1`

` => x= -1 : 3/(10)`

` => x = -10/3`