Let u=x2+y. Substitute u for all occurrences of x2+y.
Factor u2-10u+16 using the AC method.
Consider the form x2+bx+c. Find a pair of integers whose product is c and whose sum is b. In this case, whose product is 16 and whose sum is -10.
Write the factored form using these integers.
Replace all occurrences of u with x2+y.