Check 
From Example 2
Let f(x) = 2x2 + 3 and g(x) = x - 3. Find (f ° g)(3) and (g ° f)(-4)
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Solve |
Step |
| Another way | First find |
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Find (f ° g)(3) = f(g(3)) = ? |
First find g(3) |
| g(3) = 3 - 3 = 0 |
Substitute 0
into f(x) |
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f(0) = 2(0)2 + 3 = 0 + 3 = 3 |
(f ° g)(0) = 3 |
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Find (g of)(-4) = g(f(-4)) = ? |
First find f(-4) |
| f(-4) = 2(-4)2 + 3 = 2(16) + 5 = 35 |
Substitute 35
into g(x) |
| g(35) = 35 - 3 = 32 | |
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Check |
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From Example 2 |
| (f og)(x) = 2x2 - 12x + 21 |
| (f ° g)(3) = 2(3)2 - 12(3) + 21 |
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(f ° g)(3) = 18 -
36+ 12 = 3
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| (g of)(x) = 2x2 |
| (g of)(-4) = 2(-4)2 |
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(g of)(-4)
= 2(16) = 32
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