If f(x)=x^2-5x and g(x)=8-x^3, evaluate the following:
a. (f+g)(3)
b. (g-f)(4)
c. (f*)
d.(g/)

  a.  -25

  b.  -52

  c.  54

  d.  8/7 = 1 1/7

Step-by-step explanation:

Evaluate each of the functions for each of the variable values and compute the composite as defined.

a. (f+g)(3) = f(3) + g(3) = 3^2 -5·3 + 8 -3^3 = -25

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b. (g -f)(4) = g(4) -f(4) = 8 -4^3 -(4^2 -5·4) = 8 -64 -16 +20 = -52

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c. (f*g)(-1) = f(-1) · g(-1) = ((-1)^2 -5(-1)) · (8 -(-1)^3) = 6·9 = 54

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d. (g/f)(-2) = (8 -(-2)^3)/((-2)^2 -5(-2)) = (8+8)/(4+10) = 16/14 = 8/7

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Comment on approach to the problem

When there are a number of evaluations of the same function with different values of the variable, it can be convenient to let a calculator or spreadsheet do those for you.