People's Education Edition, Ninth Grade Mathematics Next Issue 13. 14.4438+06, how to do it? This requires a detailed process.

13. solution: Germany divides the triangle ABC into two equal parts, which shows that the area of triangle ADE is half that of ABC.

So the similarity ratio of triangle ADE and triangle ABC is two-thirds root sign.

That is, AD:AB= (root number 2)/2.

14. solution: m 2/n 2 (the ratio of surface area is the square of similarity ratio and the volume is the cube of similarity ratio).

16. solution: for x seconds, BD=2x, AD=8-2x.

DE| | BC So triangle ADE is similar to triangle ABC.

AD:AB = DE:BC = & gt； (8-2x):8=y:9

y = 9/8(8-2x)(0 & lt； = x & lt=4)

I hope it will be helpful to your study, and I wish you progress in your study! Hope to adopt!