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.