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Solve the simultaneous equations:

[tex]\[
\begin{cases}
\ln x = 2 \ln y \\
\ln y - \ln x = 1
\end{cases}
\][/tex]


Sagot :

Certainly! To solve the simultaneous equations given:

[tex]\[ \begin{array}{l} \ln x = 2 \ln y \quad \text{(Equation 1)} \\ \ln y - \ln x = 1 \quad \text{(Equation 2)} \end{array} \][/tex]

we will handle each equation step by step.

### Step 1: Solve for [tex]\(\ln x\)[/tex] and [tex]\(\ln y\)[/tex]

#### Equation 1:
[tex]\[ \ln x = 2 \ln y \][/tex]

Express [tex]\(\ln y\)[/tex] from this equation:
[tex]\[ \ln x = \ln y^2 \][/tex]

This implies:
[tex]\[ x = y^2 \][/tex]

#### Equation 2:
[tex]\[ \ln y - \ln x = 1 \][/tex]

Substitute [tex]\(\ln x\)[/tex] from Equation 1 into Equation 2:
[tex]\[ \ln y - 2 \ln y = 1 \][/tex]
[tex]\[ -\ln y = 1 \][/tex]
[tex]\[ \ln y = -1 \][/tex]

Solve for [tex]\(y\)[/tex]:
[tex]\[ y = e^{-1} = \frac{1}{e} \][/tex]

### Step 2: Solve for [tex]\(x\)[/tex] using the value of [tex]\(y\)[/tex]

Using the relationship [tex]\(x = y^2\)[/tex]:
[tex]\[ x = \left( \frac{1}{e} \right)^2 = \frac{1}{e^2} \][/tex]

### Step 3: Verify the solutions in both equations

Substitute [tex]\(x = \frac{1}{e^2}\)[/tex] and [tex]\(y = \frac{1}{e}\)[/tex] back into the original equations to verify they satisfy both:

#### Verify Equation 1:
[tex]\[ \ln x \stackrel{?}{=} 2 \ln y \][/tex]
[tex]\[ \ln \left( \frac{1}{e^2} \right) = 2 \ln \left( \frac{1}{e} \right) \][/tex]
[tex]\[ -2 \ln e = 2 (-\ln e) \][/tex]
[tex]\[ -2 = 2 (-1) \][/tex]
[tex]\[ -2 = -2 \][/tex]

This is true.

#### Verify Equation 2:
[tex]\[ \ln y - \ln x \stackrel{?}{=} 1 \][/tex]
[tex]\[ \ln \left( \frac{1}{e} \right) - \ln \left( \frac{1}{e^2} \right) = 1 \][/tex]
[tex]\[ -\ln e - (-2 \ln e) = 1 \][/tex]
[tex]\[ -1 + 2 = 1 \][/tex]
[tex]\[ 1 = 1 \][/tex]

This is also true.

Therefore, the values [tex]\(x = \frac{1}{e^2}\)[/tex] and [tex]\(y = \frac{1}{e}\)[/tex] are the correct solutions for the given simultaneous equations.