Why the Quran cannot be God's Word

The Quranic proposition is logically impossible. It cannot be the Word of God.

Let's state it mathematically:

X = God's Word
A = the Old Testament
B = the New Testament
C= the Quran

The Christian position is valid: X= A + B

where: B builds upon the foundation of A via progressive revelation and B is in perfect agreement with A.

The theoretical position of the Quran is also valid as stated in verses like Surah 3:3:

He has sent down upon you, [O Muhammad], the Book in truth, confirming what was before it. And He revealed the Torah and the Gospel.

where: X = A + B + C

where: C builds upon the foundation of B and A via progressive revelation and C is in perfect agreement with B and A.

However, even a cursory examination of the Quran yields the following equation:

A + B ≠ C

The Quran does not agree with the Bible.

thus since X = A + B is valid then one can only conclude that C ≠ X

In summary, if the Quran is God's word then it must be able to be harmonized with the Bible, and since it cannot be, it cannot be God's Word.