Answer:
see explanation
Step-by-step explanation:
to find f(g(x)) , substitute x = g(x) into f(x)
f(g(x))
= f(3x + 1)
= (3x + 1)² + 9(3x + 1) ← expand parenthesis
= 9x² + 6x + 1 + 27x + 9 ← collect like terms
= 9x² + 33x + 10
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to find g(f(x)), substitute x = f(x) into g(x)
g(f(x))
= g(x² + 9x)
= 3(x² + 9x) + 1 ← distribute parenthesis
= 3x² + 27x + 1
