The value of 3^2 ÷ 3 - (4^2 - 15)

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

In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.

Solve the equation by completing the square. x^2+2x=17