Explain why any parallelogram that is inscribed in a circle must be a rectangle. Draw pictures and think about the properties of both cyclic quadrilaterals and parallelograms.

Explanation:

Opposite angles of an inscribed quadrilateral are supplementary. Opposite angles of a parallelogram are congruent. Supplementary angles that are congruent must be 90°. Hence an inscribed parallelogram must be a rectangle.

you can first factor out the n to get n(1+5). we know that 1+5 is 6, so we just have 6n.