- A
- B
- C
- D
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Correct answer: A
Step 1: Find the equation of the locus S
The point of intersection is given by the solution of the two linear equations:
Our goal is to eliminate the parameter . From equation (1), we can express in terms of and : Since is a non-zero real number, .
From equation (2), we can also express : Since is non-zero, .
Now, we equate the two expressions for : Cross-multiplying gives: Using the difference of squares formula : To write this in the standard form of a conic section, we divide the entire equation by 144: This is the equation of a hyperbola. So, the locus S is a hyperbola with and .
Step 2: Find the equation of the tangent T
The tangent T is parallel to the line . The slope of this line is given by . Since T is parallel to this line, the slope of tangent T is .
The equation of a tangent to the hyperbola with slope is given by the formula: Substituting the values , , and : So, the condition for tangency is satisfied. The equations of the two possible tangents are:
Step 3: Identify the correct tangent and find p and q
The tangent T passes through the points and . This means is the x-intercept and is the y-intercept of the tangent line.
From the two possible tangent equations, the y-intercepts (when ) are and . The problem states that . Therefore, we must choose the tangent with the positive y-intercept. The equation of the tangent T is: To find the x-intercept , we set in the equation of T: Rationalizing the denominator:
Step 4: Calculate the value of pq
We have found and . Now we compute their product: This corresponds to option A.
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