英文數學工課,急要數學高手幫忙,急要答案,真的很急!!..

有咩唔明,煩請來信
以下將解答

1. f(x)=x²+2x-1
(i)
f(0)=(0)²+2(0)-1
f(0)=-1

(ii)
f(-2)=(-2)²+2(-2)-1
f(-2)=4-4-1
f(-2)=-1

(iii)
f(2x)=(2x)²+2(2x)-1
f(2x)=4x²+4x-1

(iv)
f(x+1)=(x+1)²+2(x+1)-1
f(x+1)=(x²+2x+1)+(2x+2)-1
f(x+1)=x²+4x+2

2.
f(x)=2x+1
g(x)=5-3x

g[f(-1)]
=g[2(-1)+1]
=g[-1]
=5-3(-1)
=8

3.
f(x)=x²+ax+b

﹛f(0)=-3
﹛f(2)=5

﹛(0)²+a(0)+b=-3
﹛(2)²+(2)a+b=5

﹛b=-3
﹛4+2a+b=5

﹛b=-3
﹛2a=5-4-b

把=-3代入2a=5-4-b
2a=5-4+3
a=2

∴
﹛b=-3
﹛a=2

4.
f(x)=5-2x

x│-1│0 │1 │2│ 3│
y│7 │ 5│ 3│4│-1│

f(-1)=5-2(-1)
=7

f(0)=5-2(0)
=5

f(1)=5-2(1)
=3

f(2)=5-2(2)
=4

f(3)=5-2(3)
=-1

5.
f(x)=x²-2x-3

x│-2│-1│0 │1 │2 │3│4│
y│5 │ 0│-3│-4│-3│0│5│


f(0)=5-2(0)
=-3

f(1)=5-2(1)
=-4

f(2)=5-2(2)
=-3

f(3)=5-2(3)
=0

f(4)=5-2(4)
=5

6.
f(x)=(2x+1)(x+5)
f[f(-1/2)]
=f[(2(-1/2)+1)((-1/2)+5)]
=f[(-1+1)((-1/2)+5)]
=f[0]
=(2(0)+1)((0)+5)
=5

7.
f(x)=(x+1)/(x-1)

f((x+1)/(x-1))
=((x+1)/(x-1)+1)/((x+1)/(x-1)-1)
=((x+1)+(x-1)/(x-1))/((x+1)-(x-1)/(x-1))
=((x+1)+(x-1))/((x+1)-(x-1))
=2x/2
=x

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