F.4 數學 (函數及其圖像)

2011-08-30 3:39 am

圖片參考:http://i305.photobucket.com/albums/nn203/iris993/a.jpg


圖中所示為 y=ax+b的圖像。已知△OAB 的面積12平方單位。

(a) 求 A 的坐標。
(b) 求 a 和 b 的值。
(c) (-2,4) 是否位於 y = ax + b 的圖像上?


p.s. 求式

回答 (2)

2011-08-30 3:52 am
✔ 最佳答案
Let the coordinate of point A is (x,0)

(a). 6x/2=12
x=4
(b). Gradient of the line is 6/4=3/2
So, the line is y-6=(3/2)(x-0)
y=(3/2)x+6
Compare y=(3/2)x+6 with y=ax+b,
a=3/2, b=6
(c). Substitute -2=x, 4=y
RHS=(3/2)*(-2)+6
=3
≠LHS
So, (-2,4) is NOT on the line.

2011-08-30 12:41:06 補充:
CORRECTION!!
(a). 6x/2=12
x=4
In the graph, we can see that x is negative,
so x=-4
參考: Hope I can help you! ^_^ (From me)
2011-08-30 8:11 pm
(a) A 的坐標 = ( - 4,0)


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