數學!!! 中四函數!!(初學個類)

1/
f(x)=x^2 + ax +2
f(3)=20
將3代入 f(x)
20 = 3^2 +3a +2
18 = 9 +3a
9 = 3a
a = 3

2/
f( x )=(x+k)(x-2)
f( -1 )= -1
-1 = (k -1 )( -3 )
1 / 3 = k -1
k = 4 / 3

3/ f(x)=2x+3

3a/
g(x)=f(2x)
= 2(2x)+3
=4x+3

3b/
h(x)=f(x+2)
=2(x+2)+3
=2x+4+3
=2x+7

3c/
g(x)=(1/2) h(x) -1
2 (4x+3) = 2x+7 -2
8x +6 = 2x +5
6x = 1
x = 1 / 6

1. f(x) = x^2+ax+2 (1)
f(3)=20 (2)
將(2)代人(1),得
20= 3^2+3a+2
20=11+3a
3a=9
a=3

2. f(x) =(x+k)(x-2) (1)
f(-1)=-1 (2)

將(2) 代入 (1) ,得
-1 = (-1+k)(-1-2)
-1 = 3-3k
3k=4
k=4/3

3. f(x) = 2x+3
(A) g(x) = f(2x)
g(x)=2*2x+3
g(x)=4x+3

(B) h(x)=f(x+2)
h(x)=2(x+2)+3
h(x)=2x+4+3
h(x)=2x+7

(C) g(x) = (1/2)*h (x) -1
4x+3= 1/2 * (2x+7)-1
4x+3=x+7/2-1
3x=-1/2
x=-1/6

做函數,first 將 f (x) 中 <-- x 代入 條方式中
如 f ( 1 )--> x=1, 這 條方程就係 將 x=1代入 去
f(x) = x^2 + ax +2 --> x係1 這就變成 1^2+a*1 +2
這要求個數，你未將個個f(x) = yy 這未計lo
明唔明