My Answer
Matthew's Reassurances
Matthew emphasizes the importance of the fact that Jesus fulfilled the promises of the Bible as proof that he is "the living God." God "shows himself" throughout Jesus's life, for instance when an angel appeared to his adopted earthly father Joseph in a dream about taking care of Jesus's mother Mary and Jesus. Jesus also is recorded to have risen from the dead, as any recording of any other miracle has truth. He was tested by the devil, as well. Actually, the Bible predicted what would happen in Jesus's life in many ways long ago.
Jesus saved Israel. He is fulfilling needs like people such as Abraham from the Old Testament. He ruled like King David. He makes people believe in him with the validity of the physical miracles he performed. He says Jesus is the final Messiah, though I notice He "will come again in glory." Jesus didn't discriminate against gentiles, didn't just preach to people such as the Jews themselves. Mark ties up his gospel by telling people to "go out" and help others, telling them of the good ways of being he preached to them.