Question

Tìm x, biết:

a) (x + 2)\(^2\) - (x - 3)(x + 3) = 32

b) (x - 1)\(^2\) - \(x^2\) - 4x - 4 = 0

c) (2x + 1)\(^2\) - 4(x - 1)(x + 1) = 0

Answer 1

`(x+2)^2 - (x - 3)(x+3) = 32`

`<=> x^2 + 4x + 4 - (x^2 - 3^2 ) = 32`

`<=> x^2 + 4x + 4 - x^2 + 9 - 32 = 0`

`<=> 4x - 19 = 0`

`<=> 4x = 19`

`<=> x = 19/4`

Vậy ...

`(x-1)^2 - x^2 - 4x - 4 = 0`

`<=> x^2 - 2x + 1 - x^2 - 4x - 4 = 0`

`<=> -6x - 3= 0`

`<=> -6x = 3`

`<=> x= -1/2`

Vậy ...

`(2x+1)^2 - 4(x-1)(x+1) = 0`

`<=> 4x^2 + 4x + 1 - 4(x^2 - 1)  = 0`

`<=> 4x^2 + 4x + 1 - 4x^2 + 4 = 0`

`<=> 4x + 5 = 0`

`<=> 4x = -5`

`<=> x = -5/4`

Vậy ...