-2x^2+2x+1
= -(2x^2-2x-1)
= -2(x^2-x-1/2)
= -2(x^2-2*(1/2)+(1/2)^2-3/4)
= -2(x^2-2*(1/2)+(1/2)^2)+3/2
= -2(x-1/2)^2+3
= 0
(x-1/2)^2 = 3/4
x1 = 1/2 + 根号3/2
x2 = 1/2 - 根号3/2
-2x^2+2x+1=0
-2(x^2-x-1/2)=0
x^2-x-1/2=0
x^2-x-1/2+3/4-3/4=0
x^2-x+1/4=3/4
(x-1/2)^2=3/4
x-1/2=±(√3)/2
x1=(√3+1)/2,x2=(1-√3)/2
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