When is an equation quadratic?

Answer 1

When the equation is in one the following formats:

ax2+ bx+c = 0

a(x+b)2+c = 0

(x+a)(x+b) = 0 than it is a quadric.

It is also quadratic when x2 and only x2 is in it.

example:

x2 + 1= 0 and x2=0 are quadratic equations.

However ax3+bx2+ cx+d =0 is not a quadratic, this is a cubic because of the x3 term, However you can use the quadric equation to find one of the two answers for it.