Because AB=5 AC=4, ABAC 1 is a parallelogram.

So AC = a1bad = a1d = 0.5aa1.

Let AD be X.

Because1< aa1< 9aa1= 2ad.

So 0.5 < ad < 4.5.

(2)50 is too simple to play.

(3) EO‖AC

Because EO‖AC

So Angel ·OEB = Angel ·ACB

FE‖AB HG‖AB

Angel Abbe = Angel ·HGC

Get △OBE and △HGC congruences.

It is easy to prove that ob=5.

Forget it! Do the math yourself! ! ! Play too slowly.

(4) 3.5 seconds

It is possible to solve equations without process.

You teach slowly. We have taught the function once! !