Note the Order of Persons
1. Matthew 28:19,
"Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost"
2. 2 Corinthians 13:14,
"The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen"
3. Ephesians 4:4-6
"There is one body, and one Spirit, even as ye are called in one hope of your calling; One Lord, one faith, one baptism, One God and Father of all, who is above all, and through all, and in you all."
Who, is subordinate to Who? This in itself shows that The Three are 100% COEQUAL. Take a look at the OP, where I have shown from 1 Corinthians 1:9, where God the Father is working "on behalf of" Jesus Christ. This is "subordination". In Galatians 1:1, both Jesus and the Father JOINTLY send Paul as an Apostle. Note the order of Persons here, Jesus First, then the Father. Like in John 10:28-29, "And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father's hand.". Again, Jesus is First!