`a)`
`(x+3)^2 - (x-4).(x-8) = 1`
`=> (x^2 + 2 . x . 3 + 3^2) - (x^2 - 8x - 4x + 32) = 1`
`=> (x^2 + 6x + 9) - (x^2 - 12x + 32) = 1`
`=> x^2 + 6x + 9 - x^2 + 12x - 32 = 1`
`=> 18x - 23 = 1`
`=> 18x = 24`
`=> x = 4/3`
Vậy `x = 4/3`
``
`b)`
`3 (x+2)^2 + (2x-1)^2 - 7(x+3)(x-3) = 36`
`=> 3 . (x^2 + 2 . x . 2 + 2^2) + [ (2x)^2 - 2 . 2x . 1 + 1^2] - 7 . (x^2 - 9) = 36`
`=> 3 . (x^2 + 4x +4) + (4x^2 - 4x + 1) - (7x^2 - 63) = 36`
`=> 3x^2 + 12x +12 + 4x^2 - 4x + 1 - 7x^2 + 63 = 36`
`=> 8x + 76 =36`
`=> 8x = -40`
`=> x = -5`
Vậy `x = -5`
