✔ 最佳答案
你好~~~
第一題,那個 y 應該等於 9,不是 90 吧..
1a) y^2 = k(x + b)
當 x = 8,y = 9︰
9^2 = k(8 + b)
k(8 + b) = 81..........(1)
當 x = 15,y = 12︰
12^2 = k(15 + b)
144 = k(15 + b)..........(2)
(1): k = 81 / (8 + b)..........(3)
代 (3) 進 (2):
144 = [81(15 + b)] / (8 + b)
144(8 + b) = 1215 + 81b
1152 + 144b = 1215 + 81b
144b - 81b = 1215 - 1152
63b = 63
b = 1..........(4)
1b) 代 a) 題的 (4) 進 (3)︰
k = 81 / (8 + 1)
k = 9
1c) y^2 = k(x + b)
當 x = 24︰
y^2 = 9(24 + 1)
y^2 = 225
y = 15
2a) S = kw
k = S / w
k = 50 / 350
k = 1 / 7
所以,S = (1 / 7)(w)
b) S = (1 / 7) x w
S = (1 / 7) x 637
S = 91
由於不懂打那個符號,所以就略寫了那一步,轉而先寫 k 了。
希望可以幫到你~~~~~