Which of the following are quadratic equations?
(i) x2+6x-4=0
(ii)√(3x2)-2x+1/2=0
(iii) x2+1/x2=5
(iv) x-3/x=x2
(v) 2x2-√3x+9=0
(vi) x2-2x-√x-5=0
(vii) 3x2-5x+9=x2-7x+3
(viii) x+1/x=1
(ix) x2-3x=0
(x) (x+1/x)2=3(1+1/x)+4
(xi) (2x+1)(3x+2)=6(x-1)(x-2)
(xii) x+1/x=x2, x≠0
(xiii)16x2-3=(2x+5)(5x-3)
(xiv) (x+2)3=x3-4
(xv) x(x+1)+8=(x+2)(x-2)
