(1)2x^2-4x-3=2(x^2-2x+1)-3-2=2(x-1)^2-5=[2^0.5(x-1)+5^0.5]*[2^0.5(x-1)-5^0.5]*(2)x^2-5x+5=x^2-5x+(5/2)^2-(5/2)^2+5=(x-2.5)^2-1.25=(x-2.5-0.5*5^0.5)*(x-2.5+0.5*5^0.5)解方程：（2x-1)^2-49=0 （2x-1)^2-7^...