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2. Find the equation of the tangent line to the curve. \[ y=x^{3}-2 x \quad \text { at the point when } x=-1 \]

Ask by Jimenez Hobbs. in Canada
Jan 23,2025

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Answer

The equation of the tangent line is \( y = x + 2 \).

Solution

To find the equation of the tangent line to the curve \( y = x^3 - 2x \) at the point where \( x = -1 \), follow these steps: 1. **Find the \( y \)-coordinate at \( x = -1 \):** \[ y = (-1)^3 - 2(-1) = -1 + 2 = 1 \] So, the point of tangency is \( (-1, 1) \). 2. **Find the derivative \( \frac{dy}{dx} \) to determine the slope of the tangent line:** \[ \frac{dy}{dx} = \frac{d}{dx}(x^3 - 2x) = 3x^2 - 2 \] Evaluate the derivative at \( x = -1 \): \[ \left. \frac{dy}{dx} \right|_{x = -1} = 3(-1)^2 - 2 = 3(1) - 2 = 1 \] So, the slope \( m \) of the tangent line is \( 1 \). 3. **Use the point-slope form of the equation of a line:** \[ y - y_1 = m(x - x_1) \] Plugging in the values: \[ y - 1 = 1(x - (-1)) \\ y - 1 = x + 1 \\ y = x + 2 \] **Final Answer:** \[ y = x + 2 \]

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To find the equation of the tangent line, we first need to determine the slope of the curve at \( x = -1 \). We start by differentiating the function \( y = x^3 - 2x \): \[ \frac{dy}{dx} = 3x^2 - 2 \] Now, substituting \( x = -1 \): \[ \frac{dy}{dx} \bigg|_{x=-1} = 3(-1)^2 - 2 = 3(1) - 2 = 1 \] So the slope of the tangent line at the point \( x = -1 \) is \( 1 \). Next, we find the corresponding \( y \) value at \( x = -1 \): \[ y = (-1)^3 - 2(-1) = -1 + 2 = 1 \] Thus, the point of tangency is \( (-1, 1) \). We can now use the point-slope form of the equation of a line, \( y - y_1 = m(x - x_1) \), where \( m \) is the slope and \( (x_1, y_1) \) is the point of tangency: \[ y - 1 = 1(x + 1) \] Simplifying, we obtain: \[ y = x + 2 \] So, the equation of the tangent line is \( y = x + 2 \).

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