A quadratic expression is an expression that can be in the form ax^2 + bx + c, where a, b, and c are all constants, and a does not equal 0. (ax must be squared, it can't be raised to a power other than 2)
-6x^2 + 3 and 1 - 4x^2 can be in the form ax^2 + bx + c. Therefore, they are the quadratic expressions.
