'Do You Not Know' in the Bible

Whether do you not know, that so many of us as were baptized unto Jesus Christ were baptized into His death?

Do you not know, that to whom you present yourselves servants unto obedience, ye are servants to whom you obey; whether of sin unto death, or obedience unto righteousness?

God did not cast away his people whom he foreknew. Do you not know what the scripture says in Elijah, how he makes intercession to God against Israel?