Math  /  Algebra

QuestionGiven that f(x)=x2+5xf(x)=x^{2}+5 x and g(x)=x6g(x)=x-6, calculate the following: You do not need to simplify (a) (fg)(x)=(f \circ g)(x)= \square (b) (gf)(x)=(g \circ f)(x)= \square (c) (ff)(x)=(f \circ f)(x)= \square (d) (gg)(x)=(g \circ g)(x)= \square

Studdy Solution

STEP 1

1. The notation (fg)(x) (f \circ g)(x) represents the composition of the functions f f and g g , meaning f(g(x)) f(g(x)) .
2. The function f(x)=x2+5x f(x) = x^2 + 5x is a quadratic function.
3. The function g(x)=x6 g(x) = x - 6 is a linear function.
4. We will substitute the expression for one function into the other as indicated by the composition.

STEP 2

1. Calculate (fg)(x) (f \circ g)(x) .
2. Calculate (gf)(x) (g \circ f)(x) .
3. Calculate (ff)(x) (f \circ f)(x) .
4. Calculate (gg)(x) (g \circ g)(x) .

STEP 3

To find (fg)(x) (f \circ g)(x) , substitute g(x) g(x) into f(x) f(x) :
f(g(x))=f(x6) f(g(x)) = f(x - 6)
Substitute x6 x - 6 into f(x)=x2+5x f(x) = x^2 + 5x :
f(x6)=(x6)2+5(x6) f(x - 6) = (x - 6)^2 + 5(x - 6)

STEP 4

To find (gf)(x) (g \circ f)(x) , substitute f(x) f(x) into g(x) g(x) :
g(f(x))=g(x2+5x) g(f(x)) = g(x^2 + 5x)
Substitute x2+5x x^2 + 5x into g(x)=x6 g(x) = x - 6 :
g(x2+5x)=(x2+5x)6 g(x^2 + 5x) = (x^2 + 5x) - 6

STEP 5

To find (ff)(x) (f \circ f)(x) , substitute f(x) f(x) into itself:
f(f(x))=f(x2+5x) f(f(x)) = f(x^2 + 5x)
Substitute x2+5x x^2 + 5x into f(x)=x2+5x f(x) = x^2 + 5x :
f(x2+5x)=(x2+5x)2+5(x2+5x) f(x^2 + 5x) = (x^2 + 5x)^2 + 5(x^2 + 5x)

STEP 6

To find (gg)(x) (g \circ g)(x) , substitute g(x) g(x) into itself:
g(g(x))=g(x6) g(g(x)) = g(x - 6)
Substitute x6 x - 6 into g(x)=x6 g(x) = x - 6 :
g(x6)=(x6)6 g(x - 6) = (x - 6) - 6
The solutions are: (a) (fg)(x)=(x6)2+5(x6) (f \circ g)(x) = (x - 6)^2 + 5(x - 6) (b) (gf)(x)=x2+5x6 (g \circ f)(x) = x^2 + 5x - 6 (c) (ff)(x)=(x2+5x)2+5(x2+5x) (f \circ f)(x) = (x^2 + 5x)^2 + 5(x^2 + 5x) (d) (gg)(x)=x12 (g \circ g)(x) = x - 12

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