Astudent made the following chart to prove that ab2 + bc2 = ac2. (see attachment)
which of the first four steps is the error?

Step-by-step explanation:

The first step is wrong.

It's completely wrong because in the first step the student's justification of the congruence doesn't make sense. Basically because angle BCA is not corresponding to angle BCD, the right equivalence would be between angle BCA and DCB.

So, the student is demonstrating wrong the triangles congruence, because he is establishing a congruence between angles that don't correspond, there are in different spots.

Therefore, the first step is the error.

you forgot an image

step-by-step explanation:

tube or goog would be a great resource to with that question