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QJEEM22Ma0c93: JEE Main 2022 Mathematics - Class 11 JEEM22Ma0c93 Solution: If the equation of the parabola, whose vertex is at (5, 4) and…

If the equation of the parabola, whose vertex is at (5, 4) and the directrix is 3x+y−29=03x + y - 29 = 0 , is x2+ay2+bxy+cx+dy+k=0{x^2} + a{y^2} + bxy + cx + dy + k = 0 , then a+b+c+d+ka + b + c + d + k is equal to :

Multiple Choice Options

  • A 575
  • B −- 575
  • C 576
  • D −- 576

Step-by-Step Verified Solution

Given vertex is (5, 4) and directrix 3x + y −- 29 = 0

Let foot of perpendicular of (5, 4) on directrix is (x1, y1)

x1−53=y1−41=−(−10)10{{{x_1} - 5} \over 3} = {{{y_1} - 4} \over 1} = {{ - ( - 10)} \over {10}}

∴\therefore (x1, y1)≡(8, 5)({x_1},\,{y_1}) \equiv (8,\,5)

So, focus of parabola will be S=(2,3)S = (2,3)

Let P(x, y) be any point on parabola, then

(x−2)2+(y−3)2=(3x+y−29)210{(x - 2)^2} + {(y - 3)^2} = {{{{(3x + y - 29)}^2}} \over {10}}

⇒10(x2+y2−4x−6y+13)=9x2+y2+841+6xy−58y−174x\Rightarrow 10({x^2} + {y^2} - 4x - 6y + 13) = 9{x^2} + {y^2} + 841 + 6xy - 58y - 174x

⇒x2+9y2−6xy+134x−2y−711=0\Rightarrow {x^2} + 9{y^2} - 6xy + 134x - 2y - 711 = 0

and given parabola

x2+ay2+bxy+cx+dy+k=0{x^2} + a{y^2} + bxy + cx + dy + k = 0

∴\therefore a = 9, b = −- 6, c = 134, d = −- 2, k = −- 711

∴\therefore a+b+c+d+k=−576a + b + c + d + k = - 576

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