'Believest' in the Bible

Jesus answered and said to him, Because I said to thee, I saw thee under the fig-tree, believest thou? Thou shalt see greater things than these.

and every one who lives and believes on me shall never die. Believest thou this?

Believest thou not that I am in the Father, and that the Father is in me? The words which I speak to you I do not speak from myself; but the Father who abides in me, he does the works.