How to write 8 + 9x in algebraic expression​

Which best explains why this triangle is or is not a right triangle?

25 ! the line of best fit is h = 5a + 86. predict the height at age 16. show your work.

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.