Mathieu is finding the x-intercepts of the function f(x)=x^2+4x+3. His world is shown below. (In the photo) The Answer is: (He set the factored expressions equal to each other) I learned that the hard way trial and error >~< Which error did Mathieu make? He factored incorrectly. He did not use the constant as the x-intercept. (He set the factored expressions equal to each other.) He incorrectly solved the equation x + 3 = x + 1.