7.3√2 8. 1/2 9.-5e (arrow)10.601/2 (a-b) (arrow) 12.3 65438+

15.(√5- 1)/2 16.5cm 17。 March 8 or February 3, 2008. 5/2 or 2 or 4√2-3

19. 1 20.2a-3b (arrow) 2 1. Omit 22. 1) Omit 2) ef =123.0.6m.

24. Pay attention to the fact that P is on the extension line of DA (1) in two cases. 2)y =-x ^ 2/4+3/2x(0 < x & lt； 6)y=x^2/4-3/2x(x & gt； 6) 3) Discuss PD= 14 in two cases.

25.1) y = x 2-3x+22) c (-1,-1) y = (x-3/2) 2-29/4 or c (31) y =