Which equation is NOT a quadratic equation?
y = x2 + 6x - 5
y = 2x + 5
y = 2x2 + 5
y = 4x2
@phi

Question

Which equation is NOT a quadratic equation?
    y = x2 + 6x - 5 
   y = 2x + 5 
   y = 2x2 + 5 
   y = 4x2 
@phi

primeralph · Answer

B.

primeralph · Answer

Quadratic equations have something of the order x^2

primeralph · Answer

B has only x^1.

phi · Answer

you should know quadratic means the an equation with x^2 as the highest order

in other words, quadratic means  x^2  and any lower order (x  or constant)

any guess for this question ?

phi · Answer

notice all but 1 has an x^2 as the "highest order"

primeralph · Answer

@phi Come to think of it, don't you think the definition of a quad equation in this sense if faulty?

primeralph · Answer

For example, say we define a quad as having x^2 as the highest order and we set the coeff to 0. Can we still classify B as a quad? 
Just a thought.

anonymous · Answer

thank you both i think i understand!

primeralph · Answer

You're welcome.

anonymous · Answer

@primeralph if the coefficient of x^2 then it doesn't exist, making it not the highest order...

anonymous · Answer

@primeralph also, quadratic equations are non-linear, and 2x+5 is linear

primeralph · Answer

@robz8  I do understand. I was just trying to challenge the defintion.

primeralph · Answer

*definition.