Math Problem Statement

f(x)=4x+3 and g(x)=2x2+5x, find (f∘g)(x)

Solution

To find (fg)(x)(f \circ g)(x), we need to compute f(g(x))f(g(x)), which means substituting the function g(x)g(x) into the function f(x)f(x).

Given:

  • f(x)=4x+3f(x) = 4x + 3
  • g(x)=2x2+5xg(x) = 2x^2 + 5x

Now, substitute g(x)g(x) into f(x)f(x):

(fg)(x)=f(g(x))=4(g(x))+3(f \circ g)(x) = f(g(x)) = 4(g(x)) + 3

Substitute g(x)=2x2+5xg(x) = 2x^2 + 5x into this expression:

(fg)(x)=4(2x2+5x)+3(f \circ g)(x) = 4(2x^2 + 5x) + 3

Now, distribute the 4:

(fg)(x)=8x2+20x+3(f \circ g)(x) = 8x^2 + 20x + 3

So, the composition (fg)(x)=8x2+20x+3(f \circ g)(x) = 8x^2 + 20x + 3.

Would you like more details or have any questions?

Related Questions:

  1. What is the reverse composition (gf)(x)(g \circ f)(x)?
  2. How would the result change if f(x)=2x+1f(x) = 2x + 1 instead of f(x)=4x+3f(x) = 4x + 3?
  3. What is the domain of the function (fg)(x)(f \circ g)(x)?
  4. How can you graph the function (fg)(x)(f \circ g)(x)?
  5. How do you find the composition of functions when both functions are quadratic?

Tip:

Always carefully substitute the inner function (like g(x)g(x)) into the outer function (like f(x)f(x)) when dealing with compositions!

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Polynomials

Formulas

(f ∘ g)(x) = f(g(x))
Distributive property: a(b + c) = ab + ac

Theorems

Function Composition Rule

Suitable Grade Level

Grades 9-11