'Unable' in the Bible

Then Rezin the king of Syria, and Pekah son of Remaliah, the king of Israel, came up to Jerusalem to battle; and they besieged Ahaz, but were unable to conquer him.

But I have made Esau bare, I have uncovered his secret places, that he is unable to hide himself: his seed is wasted, and his brethren, and his neighbours, and he is not.

When Ephraim saw his sickness, and Judah his sore, then went Ephraim to the Assyrian, and sent to king Jareb; but he was unable to heal you, nor hath he removed your sore.