f (x) = x* +8x+15 g (x) = x +5 find ({ •g) (x) x3 +68x2 +75 or x +13x2 +55x+ 75 or x3 +23x2 +45x+ 75 or x +13x2 +55x 55x+20
To find \((f \circ g)(x)\), we need to substitute \(g(x)\) into \(f(x)\).
### Given functions:
- \( f(x) = x^3 + 8x + 15 \)
- \( g(x) = x + 5 \)
### Finding \( (f \circ g)(x) \):
1. Compute \( g(x) \):
\[
g(x) = x + 5
\]
2. Substitute \( g(x) \) into \( f(x) \):
\[
f(g(x)) = f(x + 5)
\]
3. Now, replace \( x \) in \( f(x) \) with \( x + 5 \):
\[
f(x + 5) = (x + 5)^3 + 8(x + 5) + 15
\]
4. Calculate \( (x + 5)^3 \):
\[
(x + 5)^3 = x^3 + 3 \cdot 5 x^2 + 3 \cdot 5^2 x + 5^3
\]
\[
= x^3 + 15x^2 + 75x + 125
\]
5. Now substitute this back:
\[
f(x + 5) = [x^3 + 15x^2 + 75x + 125] + 8(x + 5) + 15
\]
\[
= x^3 + 15x^2 + 75x + 125 + 8x + 40 + 15
\]
\[
= x^3 + 15x^2 + (75x + 8x) + (125 + 40 + 15)
\]
\[
= x^3 + 15x^2 + 83x + 180
\]
### Result:
So, \((f \circ g)(x) = x^3 + 15x^2 + 83x + 180\).
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