What is the primary feature that distinguishes a quadratic equation from a linear equation?

It contains a variable raised to the second power.

It can be solved by isolating the variable.

Is the equation $4z^2 = 100$ a quadratic equation?

Yes, because it contains a variable raised to the second power.

No, because the 'bx' term is missing.

No, because it does not equal zero.

Yes, because it has an equal sign.