x 1={2+√[2？ -4× 1×(-2)]}/(2× 1)=(2+√ 12)/2= 1+√3; Of course x2= 1-√3.
(2)(x- 1)？ -2(x？ -1)=0 can't see clearly, if it is (x- 1)? -2(x？ - 1)=0
(x- 1)？ -2(x+ 1)(x- 1)= 0(x- 1)(x- 1-2x-2)= 0
(x- 1)[(x？ -2x+ 1)-2x-2]= 0(x- 1)(-x-3)= 0
(x- 1)(x？ -4x- 1)=0 x 1= 1，x= -3
X 1= 1 or x? -4x- 1=0 (using the root formula again), x2=2+√5, x3=2-√5.
(3)2x？ +1=2√3x root formula
x 1 =[2√3+√( 12-8)]/4 =(√3+ 1)/2，x2=(√3- 1)/2
(4)2(t- 1)？ +t= 1
(t- 1)(2t-2+ 1)=0
t 1= 1，t2= 1/2