Write a formal proof to prove the following conjecture to be
true or false.
If the statement is true, write a formal proof of it. If the
statement is false, provide a counterexample and a slightly
modified statement that is true and write a formal proof of your
new statement.
Conjecture: Let w, x, y, and z be single-digit numbers. The
4-digit number wxyz* is divisible by 9 if and only if 9 divides the
sum w + x +...