F4 Math一問~~~~~
2007-09-30 10:29 pm
If h (x ) =7x^2 -10x-12 and k(x) = - (5/3)x , find the values of x such that h(x)=k(7x+6) .
回答 (2)
2007-09-30 10:48 pm
✔ 最佳答案
h (x ) =7x^2 -10x-12k(7x+6) = - (5/3)*(7x+6)=-(35/3)*x-10
因為 h(x)=k(7x+6)
7x^2 -10x-12=-(35/3)*x-10
7x^2+(5/3)*x-2=0
(7x-3)(3x+2)=0
x=3/7 or x=-2/3
2007-09-30 10:48 pm
k(x) = - (5/3)x
k(7x+6)
= -(5/3)(7x+6)
= -(35/3)x - 10
when h(x) = k(7x+6)
7x^2 -10x-12 = -(35/3)x - 10
7x^2 - 10x + (35/3)x -12 + 10 = 0
7x^2 + (5/3)x - 2 = 0
21x^2 + 5x - 6 = 0
x = 3/7 or 2/3 (use qua. equation)
k(7x+6)
= -(5/3)(7x+6)
= -(35/3)x - 10
when h(x) = k(7x+6)
7x^2 -10x-12 = -(35/3)x - 10
7x^2 - 10x + (35/3)x -12 + 10 = 0
7x^2 + (5/3)x - 2 = 0
21x^2 + 5x - 6 = 0
x = 3/7 or 2/3 (use qua. equation)
參考: myself
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