（14x）^2-1=0 --- (14x-1)*(14x+1)=0 --- x=+1/14或x=-1/14
(2x)^2+12x+3^2=9^2 --- (2x+3)^2-9^2=0 ---- (2x+12)*(2x-6)=0 --- x=-6 或x=3
x^2-4x+4-3x+6+9-20=0 --- (x-2)^2-3(x-2)+9-20=0 --- (x-2-3)^2-20=0 --- x=5+20^(1/2)或x=5-20^(1/2)
2x^2+3x-3=0 --- (x+1)*(2x+1)-4=0--- x=0或x=3/2; x=1或x=1/2
(x-1)^2-5^2=0 --- (x+4)*(x-6)=0 --- x=-4或x=6
x(2x-5)-2(2x-5)=0 --- (2x-5)*(x-2)=0 ---- x=5/2或x=2
x^2+2x-4=0 --- (x+1)^2-5=0 --- (x+1+5^(1/2))*(x+1-5^(1/2))=0 --- x=-1-5^(1/2)或x=-1+5^(1/2)