You need to open the brackets to the right side such that:

`48 = x^2 + 6x`

You should move all terms to the left side such that:

`48 - x^2 - 6x = 0`

Multiplying by -1 and arranging the terms with respect to power of variable x yields:

`x^2 + 6x - 48 = 0`

Using quadratic formula yields:

`x_(1,2) = (-b+-sqrt(b^2-4ac))/(2a)`

You need to identify the coefficients a,b,c such that:

`a=1 , b = 6 , c = -48`

`x_(1,2) = (-6+-sqrt(36+192))/2 => x_(1,2) = (-6+-sqrt228)/2`

`x_(1,2) = (-6+-2sqrt57)/2 => x_(1,2) = (-3+-sqrt57)`

Hence, evaluating the solutions to the given quadratic equation yields `x_(1,2) = (-3+-sqrt57).`