Answer:
Step 3 is not correct (should be , not
Step-by-step explanation:
The expression that we have to simplify is:
We proceed step-by-step, in order to find the mistake did by Cedric:
1) First, we factorize the 5 outside:
--> this step is correct
2) We add +16 and -16 inside the brackets:
--> this step is correct
3) We rewrite the term as the square of a bynomial, which is
, so the expression becomes
--> we notice that this step is wrong: in fact, Cedric wrote
, which is not correct.
4) Now we continue: we rewrite -16+3 as -13,
5) Finally, we multiply the 5 by the terms in the bracket:
