hope this helps im sure some one else would be better at this than me.
you started off right but as your doing a quadratic you need to get your formula into a form that looks like
0 = ax^2+bx+c
so multiplying by 2 worked but then you needed to expand the bracket on the right hand side and rearrange everything to one side so you have 0 =
once thats done you just use the quadratic formula giving you two results for x