Question

Evaluate each function given that f(x)=3x^2-2x and g(x)= -8x-x. Give your answer in simplest form.

Answer 1

9514 1404 393

Answer:

• 261
• 27 (see comment)
• 3p^2 +22p +40

Step-by-step explanation:

In each case, put the function argument where the variable is and do the arithmetic (or algebra).

a) f(-9) = 3(-9)^2 -2(-9) = 3·81 +18 = 261

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b) g(-3) = -8(-3)-(-3) = 24 +3 = 27

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c) f(p+4) = 3(p+4)^2 -2(p+4)

  = 3(p^2 +8p +16) -2p -8

  = 3p^2 +22p +40

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Additional comment

The form of g(x) is unusual, leading us to suspect it might be ...

   g(x) = -8x^2 -x

In that case,

  g(-3) = -8(-3)^2 -(-3) = -8·9 +3 = -69