Question

Check whether the following are quadratic equations:
$(x-2)(x+1)=(x-1)(x+3)$

Answer 1

$(x-2)(x+1)=(x-1)(x+3)\Rightarrow x^2-x-2=x^2+2x-3\Rightarrow 3x-1=0$
It is not of the form $a{x}^2+bx+c=0$ as a = 0 in this case.
Hence, the given equation is not a quadratic equation.