Mathematics...

3x^2 + 10x + 7
= (3x+7)(x+1)

2011-04-26 18:36:53 補充：
Let C be the point of an island.
Consider triangle ABC.
tan < ABC = AC/BC
= 600 / 600
= 1
< ABC = 45 degree
So the compass bearing of ship B from ship A = N(180-90-45)W
= N45W

2011-04-26 18:36:59 補充：
I will draw a picture for you later. It is quite difficult to conceive the virtual triangle. Hope I can help you ^^

2011-04-26 18:49:14 補充：
Oh , I am not allowed to send the picture to you through email. Sorry ~

1. 3x^2+10x+7
=(3x+7)(x+1)
2. Let the island be point C. In tri. ABC, angle C obviously is 90 degree.
since AC=BC, angle A=angle B. Therefore angle A is 45 degree.
So the compass bearing is N45W.

Hope I can help you.

3x^2 +10x +7

=(3x+7)(x+1)

解 : 3x乘x=3^2
3x乘1+x乘7=10x
7乘1 = 7