(A+B- 1)(A+B+ 1)=8

[(A+B)- 1][(A+B)+ 1]= 8

The square of (A+B)-1 =8.

The square of (A+B) = the square of 8+1

The square of (A+B) =9

A+B= plus or minus 3.

2。 (1) solution

The time of free fall on the earth is

The square of t =20/4.9=400/49

T= 10 times the root number 2.

The time of free fall on the moon is

The square of t =20/0.8 1

T=9/20 times the root number 5.

(2) Solutions

Because the square of t is proportional to h.

So when h > h the land of the moon.

T land > t month

So objects on the earth fall freely and quickly.