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標題: F.4 Maths 2題 [打印本頁]

作者: billyconan 時間: 10-12-27 01:31 PM 標題: F.4 Maths 2題

我唔係好識做...thx

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https://www.2000fun.com/forum.php?mod=attachment&aid=MzY4NTE0fDFhOTk4Yjc5fDE3NTQzNDI5Mzd8MA%3D%3D

作者: asz123 時間: 10-12-28 08:57 PM

8a個題代個x入去係咁計得啦 b咪用a個答案計第9題一樣咁計

作者: 足金金猴 時間: 10-12-29 03:00 AM

8(a)
f(2x+k)-f(2x-k)=x
[(2x+k)(2x+k)+k]-[(2x-k)(2x-k)+k]=x
(2x)(2x)+4xk+k*k+k-(2x)(2x)+4xk-k*k-k=x
8xk=x
k=1/8

8(b)
f(2x+k)-k=f(2x-k)+k
f(2x+k)-f(2x-k)=k+k
x=2k
x=2(1/8)=1/4

9(a)
a is the slope
a=2
y=ax+b
8=2*2+b
b=4

9(b)
f(x)=(ax+b)(ax+b), f(x)=12
so (ax+b)(ax+b)=12
(ax)(ax)+2abx+b*b=12
2x*2x+2*2*4*x+4*4-12=0
4x*x+16x+4=0
x*x+4x+1=0
x={-4+ square root of [4*4-4(1)(1)]}/2(1)
=(-4+ 2*square root of 3)/2
=-2+square root of 3
or
x={-4- square root of [4*4-4(1)(1)]}/2(1)
=(-4- 2*square root of 3)/2
=-2-square root of 3

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