I, a Christian, of course believe that the Father, the Son and the Holy Spirit are one God. Three in One and One in Three a holy mystery unable to be simply summed up by human logic. But God has told us our human ways of thinking are not His ways:

Isaiah 55:8-9 For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.  For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts.   

However, for those who would deny the divinity of Jesus this scripture ought to be plain spoken and humanly comprehendible:

Matt. 28:18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.

God's peace be with you!