Question

Select all of the following that are quadratic equations.

Answer 1

A quadratic equation is one in which the highest exponent of x is 2.
$7x^2+14x=0$ is quadratic; the highest exponent is 2.
x³-3x²+1=0 is NOT quadratic.  The highest exponent of x is 3, not 2.
5x-7=0 is NOT quadratic.  The highest exponent of x is 1, not 2.
x²+3x-5=0 is quadratic; the highest exponent of x is 2.
x-5=9x+7 is NOT quadratic.  The highest exponent of x is 1, not 2.
x²-x=3x+7 is quadratic; the highest exponent of x is 2.