SOLUTION: HELP PLEASE. I have to know which is a quadratic equation. Why and why not. a)y=2x+5 b)y=2x^3+5y^2+3 c)y=2x^2 +5y+3 d)y=2x^3+5 Thank you so much for your help!

That's a LINEAR equation, not a QUADRATIC equation because
the highest power of the variable x is the first power.  
That is, it has degree 1. A QUADRATIC equation must have 
degree 2 which means it must have 2 as its highest power of
the variable x.

That's a CUBIC equation, not a QUADRATIC equation because
the highest power of the variable x is the 3rd power.  
That is, it has degree 3. A QUADRATIC equation must have 
degree 2 which means it must have 2 as its highest power of
the variable x.

That's a QUADRATIC equation, because the highest power of 
the variable x is the 2nd power.  It has degree 2. 

That's another CUBIC equation, not a QUADRATIC equation
because the highest power of the variable x is the 3rd power.

Edwin