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The function gg is defined as g(x)=ln(x2),xR,x<0g(x) = \ln(x^2), x \in \mathbb{R}, x < 0. (i) State the domain and range of gg. (ii) Give a reason why g1g^{-1} exists. (iii) Find the rule, domain and range of g1g^{-1}.

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Q. The function gg is defined as g(x)=ln(x2),xR,x<0g(x) = \ln(x^2), x \in \mathbb{R}, x < 0. (i) State the domain and range of gg. (ii) Give a reason why g1g^{-1} exists. (iii) Find the rule, domain and range of g1g^{-1}.
  1. Define function gg: The function gg is defined as g(x)=ln(x2)g(x) = \ln(x^2) for x<0x < 0. To find the domain of gg, we need to consider the values of xx for which ln(x2)\ln(x^2) is defined.\newlineSince the natural logarithm function, ln(x)\ln(x), is defined for x>0x > 0, and x2x^2 is always positive for gg00, the domain of gg is all negative real numbers.
  2. Find domain of \newlinegg: The range of \newlinegg is the set of all possible output values. Since the natural logarithm function can take any real number as its output, and \newlinex2x^2 maps any negative \newlinexx to a positive number, the range of \newlinegg is all real numbers.
  3. Find range of gg: To give a reason why the inverse of gg exists, we need to check if gg is a one-to-one function. A function is one-to-one if each output is the result of exactly one input. Since the derivative of g(x)=ln(x2)g(x) = \ln(x^2) is g(x)=2xg'(x) = \frac{2}{x}, which is always negative for x<0x < 0, gg is strictly decreasing on its domain. Therefore, gg is one-to-one and an inverse function g1g^{-1} exists.
  4. Check one-to-one function: To find the rule of the inverse function g1g^{-1}, we set y=ln(x2)y = \ln(x^2) and solve for xx in terms of yy. We exponentiate both sides to remove the natural logarithm, getting ey=x2e^y = x^2. Since we know xx is negative (from the domain of gg), we take the negative square root to find xx. Thus, x=eyx = -\sqrt{e^y}, and the rule for g1g^{-1} is y=ln(x2)y = \ln(x^2)00.
  5. Find rule of inverse function: The domain of the inverse function g1g^{-1} is the range of the original function gg, which is all real numbers, as we have established earlier.
  6. Domain of inverse function: The range of the inverse function g1g^{-1} is the domain of the original function gg, which is all negative real numbers.

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