PROBLEM
2. Given that g(x)=21x+9 and h(x)=(x+1)(x−1), determine the following. Simplify where possible.
a. h(x)−g(x) [1 mark]
b. h×g(x) [2 marks]
c. gh(x) [1 mark]
d. g∘h(x) [2 marks]
e. h∘g(x) [2 marks]
STEP 1
1. We are given two functions g(x)=21x+9 and h(x)=(x+1)(x−1).
2. We need to perform operations on these functions as specified in parts a through e.
3. Simplification of expressions is required where possible.
STEP 2
1. Calculate h(x)−g(x).
2. Calculate h×g(x).
3. Calculate gh(x).
4. Calculate the composition g∘h(x).
5. Calculate the composition h∘g(x).
STEP 3
Calculate h(x)−g(x).
First, find h(x):
h(x)=(x+1)(x−1)=x2−1 Now subtract g(x):
h(x)−g(x)=(x2−1)−(21x+9) Simplify the expression:
h(x)−g(x)=x2−21x−10
STEP 4
Calculate h×g(x).
Multiply h(x) and g(x):
h(x)×g(x)=(x2−1)×(21x+9) Distribute:
=x2×21x+x2×9−1×21x−1×9 =21x3+9x2−21x−9
STEP 5
Calculate gh(x).
Divide h(x) by g(x):
g(x)h(x)=21x+9x2−1 This expression is already simplified as much as possible.
STEP 6
Calculate the composition g∘h(x).
Substitute h(x) into g(x):
g(h(x))=g(x2−1) =21(x2−1)+9 Simplify:
=21x2−21+9 =21x2+217
SOLUTION
Calculate the composition h∘g(x).
Substitute g(x) into h(x):
h(g(x))=h(21x+9) =(21x+9+1)(21x+9−1) Simplify:
=(21x+10)(21x+8) Expand:
=(21x)2+(21x)(8)+10(21x)+80 =41x2+4x+5x+80 =41x2+9x+80
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