Math Problem Statement

f(x) = x^2 - 4x + 3, g(x) = 2x - 1. Solve (i) f(x) = 0, (ii) f(x) = g(x), (iii) g(f(-2)), (iv) f(g(x)).

Solution

Given Information:

  1. f(x)=x24x+3f(x) = x^2 - 4x + 3
  2. g(x)=2x1g(x) = 2x - 1

We are solving the following tasks:
(i) Solve f(x)=0f(x) = 0
(ii) Solve f(x)=g(x)f(x) = g(x)
(iii) Find g(f(2))g(f(-2))
(iv) Find f(g(x))f(g(x))


Solution:

(i) Solve f(x)=0f(x) = 0:

Set f(x)=x24x+3=0f(x) = x^2 - 4x + 3 = 0.
Factorizing the quadratic:
x24x+3=(x1)(x3)=0x^2 - 4x + 3 = (x - 1)(x - 3) = 0
So, x=1x = 1 and x=3x = 3.

(ii) Solve f(x)=g(x)f(x) = g(x):

Equate f(x)=g(x)f(x) = g(x):
x24x+3=2x1x^2 - 4x + 3 = 2x - 1
Rearrange terms:
x26x+4=0x^2 - 6x + 4 = 0
Factorizing x26x+4x^2 - 6x + 4 using the quadratic formula:
x=b±b24ac2awhere a=1,b=6,c=4x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \quad \text{where } a = 1, b = -6, c = 4 x=(6)±(6)24(1)(4)2(1)=6±36162=6±202=6±252x = \frac{-(-6) \pm \sqrt{(-6)^2 - 4(1)(4)}}{2(1)} = \frac{6 \pm \sqrt{36 - 16}}{2} = \frac{6 \pm \sqrt{20}}{2} = \frac{6 \pm 2\sqrt{5}}{2} x=3±5x = 3 \pm \sqrt{5}
Thus, x=3+5x = 3 + \sqrt{5} and x=35x = 3 - \sqrt{5}.

(iii) Find g(f(2))g(f(-2)):

First, calculate f(2)f(-2):
f(2)=(2)24(2)+3=4+8+3=15f(-2) = (-2)^2 - 4(-2) + 3 = 4 + 8 + 3 = 15
Now substitute f(2)=15f(-2) = 15 into g(x)g(x):
g(15)=2(15)1=301=29g(15) = 2(15) - 1 = 30 - 1 = 29
So, g(f(2))=29g(f(-2)) = 29.

(iv) Find f(g(x))f(g(x)):

Substitute g(x)=2x1g(x) = 2x - 1 into f(x)f(x):
f(g(x))=f(2x1)f(g(x)) = f(2x - 1)
f(2x1)=(2x1)24(2x1)+3f(2x - 1) = (2x - 1)^2 - 4(2x - 1) + 3
Expand (2x1)2(2x - 1)^2:
(2x1)2=4x24x+1(2x - 1)^2 = 4x^2 - 4x + 1
Substitute into f(g(x))f(g(x)):
f(g(x))=4x24x+18x+4+3f(g(x)) = 4x^2 - 4x + 1 - 8x + 4 + 3
Simplify:
f(g(x))=4x212x+8f(g(x)) = 4x^2 - 12x + 8
So, f(g(x))=4x212x+8f(g(x)) = 4x^2 - 12x + 8.


Final Answers:

(i) x=1x = 1, x=3x = 3
(ii) x=3+5x = 3 + \sqrt{5}, x=35x = 3 - \sqrt{5}
(iii) g(f(2))=29g(f(-2)) = 29
(iv) f(g(x))=4x212x+8f(g(x)) = 4x^2 - 12x + 8

Do you want details for any step?

Here are 5 related questions to deepen your understanding:

  1. How do we determine the roots of a quadratic equation using factorization?
  2. What is the quadratic formula, and when is it used?
  3. How can we verify the solutions of f(x)=g(x)f(x) = g(x)?
  4. What happens if g(x)g(x) is a higher-degree polynomial?
  5. How do we interpret f(g(x))f(g(x)) in the context of composition of functions?

Tip: Always check your solutions by substituting them back into the original equations!

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Function Composition
Roots of Equations

Formulas

Quadratic equation formula: ax^2 + bx + c = 0
Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a
Function composition: f(g(x))

Theorems

Quadratic Formula Theorem

Suitable Grade Level

Grades 9-11