A.Maths. Exam

Echo21

細薯

落雷  在 2004-10-27 07:01 PM 發表:

I'm afraid you of wrong typing of queation

don't be afraid~
i have typed the correct question!

does anyone have the A.Maths Textbook of the name called "New Trend Additional Mathematics Volume One"??
my question is come from P.6 , Classwork 5

++++++++++++++++++++++++++++++++++++++++++++++
testing

5<SUP>2</SUP>

haha~~funny~qq~XDD

[ Last edited by smallpotato226 on 2004-10-30 at 09:27 AM ]

抹茶可樂

Let f(x) = (16-k)x^2 +12x -k , where k is a constant.
a) Find the discriminant of f(x)=0 .
b) Find the condition of k such that f(x)≧0 for all real values of x .

fish

smallpotato226  在 2004-10-28 01:06 PM 發表:

don't be afriad~
i have typed the correct question!

does anyone have the A.Maths Textbook of the name called "New Trend Additional Mathematics Volume One"??
my question is come from  ...

afriad＜－－－－afraid ....."

細薯

fish  在 2004-10-29 10:49 PM 發表:

afriad＜－－－－afraid ....."

改了.......(成日錯><)

Ronald0077

落雷  在 2004-10-29 10:46 PM 發表:

Let f(x) = (16-k)x^2 +12x -k , where k is a constant.
a) Find the discriminant of f(x)=0 .
b) Find the condition of k such that f(x)≧0 for all real values of x .

a) Δ = b² - 4ac
       = 12² - 4(16-k)(-k)
       = 144 + 64k - 4k²

b) As f(x) ≧ 0, Δ ≦ 0 and 16-k ＞ 0
                      144 + 64k - 4k²≦0 and k＜16
                      k² - 16k - 36 ≧ 0 and k＜16
                      (k - 18)(k + 2) ≧ 0 and k＜16
                      (k ≦ -2 or k ≧ 18) and k＜16
                   ∴k ≦ -2

see if sth wrong @@~