Geometry help please

What number should be added to the expression x^2+3x+ in order to create a perfect square trinomial? 3/2 3 9/4 9

Is this a polynomial function? i need to know asap

Select the correct answer from each drop-down menu. the length of a rectangle is 5 inches more than its width. the area of the rectangle is 50 square inches. the quadratic equation that represents this situation is the length of the rectangle is inches.