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14 votes
5, 3.1.24

f(x) = 3x² + 5; find f(x + 3) - [f(x) + 3]

User PC Luddite
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1 Answer

14 votes
14 votes

Given that
f(x) = 3x^2 + 5, we have


f(x + 3) = 3 (x + 3)^2 + 5 \\\\= 3 (x^2 + 6x + 9) + 5 \\\\= 3x^2 + 18x + 32

so that


f(x+3) - (f(x) + 3) = (3x^2 + 18x + 32) - (3x^2 + 8) \\\\= \boxed{18x + 24}

User Areller
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