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Q.A point R with x-coordinate 4 lies on the line joining the points P(2, -3, 4) and Q(8, 0, 10). Find the ratio PR : RQ and the coordinates of R. OR Find the area of the triangle formed by the lines joining the vertex of the parabola x² = 12y to the end of the latus rectum.

Haryana BsehBoard of School Education Haryana (Senior Secondary Part-I / Class 11) 2026Subjective· 5mImportance★★★★★
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Let R divide PQ in ratio k:1, use the x-coordinate condition to solve for k, then find the y- and z-coordinates using the section formula.

Let RR divide the segment PQPQ (with P(2,−3,4)P(2,-3,4), Q(8,0,10)Q(8,0,10)) in the ratio k:1k:1 (i.e. PR:RQ=k:1PR:RQ = k:1).

By the section formula, the x-coordinate of RR is:

xR=k(8)+1(2)k+1=4x_R = \frac{k(8)+1(2)}{k+1} = 4

Solve for kk:

8k+2=4(k+1)=4k+4  ⟹  4k=2  ⟹  k=128k+2 = 4(k+1) = 4k+4 \implies 4k=2 \implies k=\frac12

So PR:RQ=12:1=1:2PR:RQ = \dfrac12 : 1 = 1:2.

Find y and z using k=12k=\dfrac12: …

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