Multiple choice Which of the following is not a quadratic equation? $2(x-1)^2=4x^2-2x+1$ $(x^2+1)^2=x^2+3x+9$ $(x^2+2x)^2=x^4+3+4x^3$ $x^2+9=3x^2-5x$ Reveal answer Fill a bubble to check yourself B Correct answer Explanation A quadratic equation must have a degree of 2. In option B, expanding (x^2+1)^2 results in x^4 + 2x^2 + 1, which leads to a degree of 4, making it not a quadratic equation.