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← JEE Main 2022 · 29 Jul · Shift 1
MathematicsInteger+4 / -1Question 23 of 90

JEE Main 2022 · 29 Jul · Shift 1, Mathematics question 23

Let a line with direction ratios a, −4a, −7 be perpendicular to the lines with direction ratios 3, −1, 2b and b, a, −2. If the point of intersection of the line x+1a2+b2=y−2a2−b2=z1\dfrac{x+1}{a^2+b^2}=\dfrac{y-2}{a^2-b^2}=\dfrac z1 and the plane x−y+z=0x-y+z=0 is (α, β, γ), then α + β + γ is equal to _______.

Answer and worked solution

Official answer: 10

Perpendicularity. 3a+4a−14b=03a+4a-14b=0 gives a=2ba=2b; ab−4a2+14=0ab-4a^2+14=0 gives b2=1b^2=1, a2=4a^2=4.

Line (−1+5t, 2+3t, t)(-1+5t,\,2+3t,\,t) meets x−y+z=0x-y+z=0 at t=1t=1: (4,5,1)(4,5,1), sum 10.

Answer: 10