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Multiple Choice
How many tangent lines to the curve pass through the point ?
A
B
C
D
Verified step by step guidance
1
Step 1: Begin by finding the derivative of the given curve y = x/(x + 1) to determine the slope of the tangent line at any point on the curve. Use the quotient rule: \( \frac{d}{dx} \left( \frac{u}{v} \right) = \frac{u'v - uv'}{v^2} \), where \( u = x \) and \( v = x + 1 \).
Step 2: Apply the quotient rule to compute \( \frac{dy}{dx} \). Substitute \( u = x \), \( u' = 1 \), \( v = x + 1 \), and \( v' = 1 \) into the formula: \( \frac{dy}{dx} = \frac{(1)(x + 1) - (x)(1)}{(x + 1)^2} \). Simplify the expression to find the slope of the tangent line at any point \( x \).
Step 3: Write the equation of the tangent line in point-slope form: \( y - y_1 = m(x - x_1) \), where \( m \) is the slope \( \frac{dy}{dx} \), and \( (x_1, y_1) \) is a point on the curve. Substitute \( y_1 = \frac{x_1}{x_1 + 1} \) (from the curve equation) and \( m = \frac{dy}{dx} \).
Step 4: Determine the condition for the tangent line to pass through the external point (1, 1/2). Substitute \( x = 1 \) and \( y = 1/2 \) into the tangent line equation. Solve for \( x_1 \), which represents the x-coordinate of the point of tangency on the curve.
Step 5: Solve the resulting equation for \( x_1 \). This will yield the x-coordinates of the points on the curve where the tangent lines pass through (1, 1/2). Verify that there are two distinct solutions for \( x_1 \), confirming that there are two tangent lines.