Solve (algebraically by any method) 3x to the 2 power +8x - 4= 0

3 x^{2} + 8x +(-4) = 0
x = -b + √ b² - 4ac
               2a
x = -8 + √ 8² - 4(3)(-4)
                 2(3)
x = -8 + √64 - 48
               6
x = -8 + √16
           6
x = -8 + 4       x = -8 - 4
         6                    6
x = -4              x = -12
      6                       6    
x = -2              x = -2
      3  

What is the diagram u didn't post that