Y is the sum of two parts. One part varies directly as x, while the other part varies directly as x^2. Y= -33 when x=3 and Y= -48 when x=6
(a) Express Y in terms of x.
(b) Find the minimum possible value of Y when x varies.
Variation questions
2010-02-02 8:33 pm
回答 (1)
2010-02-02 8:44 pm
✔ 最佳答案
a)Let Y = k1 x + k2 x^2-33 = k1 *3 + k2 *3^2......(1)
-48 = k1 *6 + k2 *6^2......(2)
(2) - (1)*2 :
-48 + 66 = 36k2 - 18k2
k2 = 1 , sub it to (1) :
-33 = k1 *3 + 3^2
k1 = - 14
So Y = -14x + x^2
b)Y = -14x + x^2
= x^2 - 2(7)x + 7^2 - 7^2
= (x - 7)^2 - 49
When x = 7
The minimum possible value of Y = - 49
收錄日期: 2021-04-21 22:08:33
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100202000010KK03750