Math Problem Statement

Let f(x) = √(5 + x) and g(x) = √(5 - x). Find the domains of f + g, f - g, f * g, and f / g.

Solution

We are given two functions:

f(x)=5+xf(x) = \sqrt{5 + x} and g(x)=5xg(x) = \sqrt{5 - x}.

To solve the domain-related problems in the image, we need to determine the domain for each case.

(a) The domain of f+gf + g:

The domain of the sum of two functions is the intersection of the domains of f(x)f(x) and g(x)g(x).

  • The domain of f(x)=5+xf(x) = \sqrt{5 + x}: The expression inside the square root, 5+x5 + x, must be non-negative: 5+x0    x5.5 + x \geq 0 \implies x \geq -5. Therefore, the domain of f(x)f(x) is [5,)[-5, \infty).

  • The domain of g(x)=5xg(x) = \sqrt{5 - x}: The expression inside the square root, 5x5 - x, must also be non-negative: 5x0    x5.5 - x \geq 0 \implies x \leq 5. Therefore, the domain of g(x)g(x) is (,5](-\infty, 5].

The domain of f+gf + g is the intersection of the domains of ff and gg, which is: [5,5].[-5, 5].

(b) The domain of fgf - g:

Similar to part (a), the domain of fgf - g is the intersection of the domains of ff and gg. Therefore, it remains: [5,5].[-5, 5].

(c) The domain of fgf \cdot g (product):

Again, the domain of the product of two functions is the intersection of the domains of ff and gg. Thus, the domain of fgf \cdot g is: [5,5].[-5, 5].

(d) The domain of fg\frac{f}{g} (quotient):

The domain of the quotient fg\frac{f}{g} is the intersection of the domains of f(x)f(x) and g(x)g(x), excluding any points where g(x)=0g(x) = 0, since division by zero is undefined.

  • We already know that the domain of both f(x)f(x) and g(x)g(x) is [5,5][-5, 5].
  • Set g(x)=0g(x) = 0 to find where it is undefined: 5x=0    5x=0    x=5.\sqrt{5 - x} = 0 \implies 5 - x = 0 \implies x = 5. Therefore, g(x)=0g(x) = 0 when x=5x = 5.

Thus, the domain of fg\frac{f}{g} is [5,5)[-5, 5) (excluding x=5x = 5).

Final Answers:

  • (a) The domain of f+gf + g is [5,5][-5, 5].
  • (b) The domain of fgf - g is [5,5][-5, 5].
  • (c) The domain of fgf \cdot g is [5,5][-5, 5].
  • (d) The domain of fg\frac{f}{g} is [5,5)[-5, 5).

Would you like any further details or clarifications on these results?

Here are five related questions you might consider:

  1. How does the square root function impact the domain of a function?
  2. What changes would occur in the domain if f(x)f(x) and g(x)g(x) involved higher powers?
  3. What happens to the domain if g(x)g(x) were placed in the numerator instead?
  4. How would the domains change if f(x)f(x) and g(x)g(x) were logarithmic functions instead of square root functions?
  5. How can we graphically interpret the domains of these functions?

Tip: Always check for points where the denominator equals zero when working with quotient functions to avoid undefined values.

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Math Problem Analysis

Mathematical Concepts

Domain of functions
Square root functions
Addition, subtraction, product, and quotient of functions

Formulas

f(x) = √(5 + x)
g(x) = √(5 - x)
Domain of sum, difference, product, and quotient of functions

Theorems

For square root functions, the expression inside the square root must be non-negative. For quotients, the denominator cannot be zero.

Suitable Grade Level

Grades 10-12