Question

Select all of the following that are quadratic equations.

7x2 + 14x = 0
x3 - 3x2 + 1 = 0
5x - 7 = 0
x2 + 3x -5 = 0
x - 5 = 9x + 7
x2 - x = 3x + 7

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.