What is the answer of 5/6 -3/6

Which of the following constants can be added to x2 - 3x to form a perfect square trinomial?

An eagle is flying at a constant height of 1000root3 meters from the ground level . a boy standing on the ground observes the angle of elevation of the eagles as 45. after 15 seconds it's angle becomes 30. find it's speed in km/hr

The eagle club wants to build a chain of 2,505 dominoes. if they have already set up 807 dominoes, how many more do they need to add to meet their goal?