Help please​

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Sketch the vector field vector f( vector r ) = 8vector r in the xy-plane. select all that apply. the length of each vector is 8. the lengths of the vectors decrease as you move away from the origin. all the vectors point away from the origin. all the vectors point in the same direction. all the vectors point towards the origin. the lengths of the vectors increase as you move away from the origin.

In trapezoid abcd, ac is a diagonal and ∠abc≅∠acd. find ac if the lengths of the bases bc and ad are 12m and 27m respectively.