Which equation is a proportion?

Find the domain of the function  [tex]f(x) = \sqrt{3x - 7} [/tex]in interval form, the domain of f is what? in advance.

Which statement is not always true for a parallelogram? (a) opposite sides are congruent. (b) diagonals bisect each other. (c) it has 4 congruent angles. (d) consecutive angles are supplementary.

Need on this geometry question. explain how you did it.