1. The equation is .
  2. The equation is .
  3. The equation is .
  4. The equation is .
We will check the degree of each equation:
  1. This is a quadratic equation because there is a term.
  2. This is a linear equation because the highest exponent is one.
  3. This is neither linear nor quadratic because it has a degree of three.
  4. This is a linear equation because it has a degree of one. The coefficient is irrational, but the variable is not in the square root.