數學qraduatic equation~~

a(i)
2x^2 +2x - 1 = 0
x = {-2√[ 2^2 - 4(2)(-1)]} /[2(2)]
x = (-1 √3)/2
(a)(ii)
2x^2 + 2ax-a^2 = 0
x = {-2a √[(2a)^2 - 4(2)(-a^2)] }/[2(2)]
x = (-aa√3)/2
= (-1 √3)a/2
(b)
4x^3 +5x^2 - x = 0
x(4x^2 +5x - 1) = 0
x = 0 or 4x^2 +5x - 1 = 0
x= 0 or x = {-5√[5^2 - 4(4)(-1)]}/ [2(4)]
x = 0 or x = (-5√41)/8