The function g is defined by g:x↦ln⁡(x−3)g : x \mapsto \ln\bigl(x - \sqrt{3}\bigr), for x∈Rx \in \mathbb{R}, x>3x > \sqrt{3}.

  1. (a)

    Explain how you know g−1g^{-1} exists.

  2. (b)

    Find g−1(x)g^{-1}(x) and write down its domain.

  3. (c)

    Solve g(x)=0g(x) = 0 exactly.

  4. (d)

    Hence, without using a calculator, solve the inequality g(x)(x−3)(x+1)≥0.\dfrac{g(x)}{(x-3)(x+1)} \ge 0.

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

8(a)

1. Show algebraically that the function is one-to-one.

Let g(x1)=g(x2)g(x_1) = g(x_2) for x1,x2>3x_1, x_2 > \sqrt{3}.
ln⁡(x1−3)=ln⁡(x2−3)\ln(x_1 - \sqrt{3}) = \ln(x_2 - \sqrt{3})
x1−3=x2−3x_1 - \sqrt{3} = x_2 - \sqrt{3}
x1=x2x_1 = x_2
Since g(x1)=g(x2)g(x_1) = g(x_2) strictly implies x1=x2x_1 = x_2, the function gg is a one-to-one function.

2. State the conclusion linking the one-to-one property to the existence of an inverse.

An inverse function exists if and only if the function is one-to-one. Therefore, g−1g^{-1} exists.

Answer

Since g(x1)=g(x2)  ⟹  x1=x2g(x_1) = g(x_2) \implies x_1 = x_2, gg is a one-to-one function. Therefore, g−1g^{-1} exists.

8(b)

1. Set up an equation and make $x$ the subject to find the inverse function.

Let y=ln⁡(x−3)y = \ln(x - \sqrt{3}).
ey=x−3e^y = x - \sqrt{3}
x=ey+3x = e^y + \sqrt{3}

2. State the inverse function in terms of $x$.

g−1(x)=ex+3g^{-1}(x) = e^x + \sqrt{3}

3. Determine the domain of $g^{-1}$ by evaluating the range of $g$.

The domain of g−1g^{-1} is the range of gg.
Given the domain of gg is x>3x > \sqrt{3}, the expression (x−3)(x - \sqrt{3}) takes all positive real values.
Therefore, the range of ln⁡(x−3)\ln(x - \sqrt{3}) is all real numbers.
Domain of g−1g^{-1} is x∈Rx \in \mathbb{R}.

Answer

g−1(x)=ex+3g^{-1}(x) = e^x + \sqrt{3}, Domain: x∈Rx \in \mathbb{R}

8(c)

1. Set the function to zero and convert the logarithmic equation to an exponential equation.

ln⁡(x−3)=0\ln(x - \sqrt{3}) = 0
x−3=e0x - \sqrt{3} = e^0
x−3=1x - \sqrt{3} = 1

2. Solve for $x$ and state the exact value.

x=1+3x = 1 + \sqrt{3}

Answer

x=1+3x = 1 + \sqrt{3}

8(d)

1. Find the critical values from the numerator and denominator.

First, we concisely reproduce the result of part (c) by solving g(x)=0g(x) = 0:
ln⁡(x−3)=0  ⟹  x−3=e0=1  ⟹  x=1+3\ln(x - \sqrt{3}) = 0 \implies x - \sqrt{3} = e^0 = 1 \implies x = 1 + \sqrt{3}
Next, we find the critical values of the denominator by setting it to zero:
(x−3)(x+1)=0  ⟹  x=3orx=−1(x-3)(x+1) = 0 \implies x = 3 \quad \text{or} \quad x = -1

2. Analyse the sign of the rational expression within the domain of the function.

The domain of g(x)g(x) is given as x>3x > \sqrt{3}. Therefore, x=−1x = -1 is rejected since it falls outside the domain, and we note that x+1>0x + 1 > 0 for all valid xx.
We test the signs of the expression g(x)(x−3)(x+1)\dfrac{g(x)}{(x-3)(x+1)} across the intervals defined by the valid critical values x=1+3x = 1 + \sqrt{3} and x=3x = 3:

  • For 3<x<1+3\sqrt{3} < x < 1 + \sqrt{3}: g(x)<0g(x) < 0 and x−3<0x - 3 < 0, so the expression is positive.
  • For 1+3<x<31 + \sqrt{3} < x < 3: g(x)>0g(x) > 0 and x−3<0x - 3 < 0, so the expression is negative.
  • For x>3x > 3: g(x)>0g(x) > 0 and x−3>0x - 3 > 0, so the expression is positive.

3. State the final solution for the inequality.

The inequality requires the rational expression to be greater than or equal to 00.
At x=1+3x = 1 + \sqrt{3}, the numerator is 00, making the expression exactly 00, which satisfies the inequality. At x=3x = 3, the expression is undefined.
Combining this with the sign analysis, we obtain the final solution:
3<x≤1+3orx>3\sqrt{3} < x \le 1 + \sqrt{3} \quad \text{or} \quad x > 3

Answer

3<x≤1+3orx>3\sqrt{3} < x \le 1 + \sqrt{3} \quad \text{or} \quad x > 3

AI analysis — may contain mistakes.

Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.

More questions on this topic

  1. 1The functions ff and gg are defined by f:x↦16−4x,  x∈R,  x≤4,f : x \mapsto \sqrt{16 - 4x},\; x \in \mathbb{R},\; x \le 4, g:x↦x2,  x∈R.g : x \mapsto x^{2},\; x \in \mathbb{R}.…
  2. 2The function g\text{g} is defined by g:x→sin⁡x+x\text{g} : x \to \sin x + x, for x∈Rx \in \mathbb{R}, −π≤x≤π-\pi \le x \le \pi. Show…
  3. 3The function gg is defined by g:x↦ln⁡(x−3)g : x \mapsto \ln(x - \sqrt{3}), for x∈Rx \in \mathbb{R}, x>3x > \sqrt{3}. Explain how yo…
  4. 4The function ff is defined by f:x↦x2−4x, x∈R, ∣x∣<1.f : x \mapsto x^2 - 4x,\ x \in \mathbb{R},\ |x|<1. The function gg is defined by g:x↦1+1x+3, x∈R, x≠−3.g : x \mapsto 1 + \frac{1}{x+3},\ x \in \mathbb{R},\ x \ne -3.…
  5. 5The function f, with domain the set of all real values, is given by f(x)={4−x2for 0<x≤2,2x−4for 2<x≤4,\text{f}(x) = \begin{cases} 4 - x^2 & \text{for } 0 < x \le 2, \\ 2x - 4 & \text{for } 2 < x \le 4, \end{cases}…