Identify which equation is a quadratic equation.

a. y = 3x + 4
b. y + x2 = (x − 2)(x + 7)
c. y = −4x(x − 4) + 2x
d. y + 3 = (x + 12)(x2 + 2)

Question

Identify which equation is a quadratic equation.

	 a. y = 3x + 4	
	 b. y + x2 = (x − 2)(x + 7)	
	 c. y = −4x(x − 4) + 2x	
	 d. y + 3 = (x + 12)(x2 + 2)

precal · Answer

quadratic equations are x^2 type
careful they are trying to trick you
d   for example if you distribute x and x^2 you get x^3 and it is a cubic and not a quadratic

anonymous · Answer

thanks!!!

e.mccormick · Answer

Yes, it is things in the form of $ax^2+bx+c=0$ where a never is 0.  Because b and c can be 0, those can go away.  That is a little more like the traditional definition than what Precal pointed out.

precal · Answer

yes  I was just pointing out the main idea

e.mccormick · Answer

Yep, all good.  So if you just take every option and use algebra to get it to that basic form, the answer should be obvious.