Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Straight Lines and Pair of Straight Lines question

2022 · 25 Jul · Shift 1 · Q32
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Mathematics
  4. /Straight Lines and Pair of Straight Lines
  5. /2022 · 25 Jul · Shift 1 · Q32

Straight Lines and Pair of Straight Lines question

2022 · 25 Jul · Shift 1 · Q32

JEE MainMathematicsStraight Lines and Pair of Straight LinesMCQ+4 / −1
A line, with the slope greater than one, passes through the point A(4,3)A(4,3)A(4,3) and intersects the line x−y−2=0x-y-2=0x−y−2=0 at the point B. If the length of the line segment ABA BAB is 293\frac{\sqrt{29}}{3}329​​, then BBB also lies on the line :
  1. A
    2x+y=92 x+y=92x+y=9
  2. B
    3x−2y=73 x-2 y=73x−2y=7
  3. C
    x+2y=6x+2 y=6x+2y=6
  4. D
    2x−3y=32 x-3 y=32x−3y=3
View written solutionFree

Correct answer: C

  1. Given data
  • Point A(4,3)A(4,3)A(4,3)
  • Point BBB lies on the line x−y−2=0  ⟹  y=x−2x-y-2=0 \implies y=x-2x−y−2=0⟹y=x−2
  • Length AB=293AB=\frac{\sqrt{29}}{3}AB=329​​
  • The line through AAA and BBB has slope greater than 111.

We need to find the coordinates of BBB, then check which option it satisfies.


  1. Let coordinates of BBB be

Since BBB lies on y=x−2y=x-2y=x−2, let B=(t,t−2)B=(t,t-2)B=(t,t−2)


  1. Use distance formula

Distance between A(4,3)A(4,3)A(4,3) and B(t,t−2)B(t,t-2)B(t,t−2) is AB2=(t−4)2+((t−2)−3)2AB^2=(t-4)^2+((t-2)-3)^2AB2=(t−4)2+((t−2)−3)2 =(t−4)2+(t−5)2=(t-4)^2+(t-5)^2=(t−4)2+(t−5)2

Given AB=293AB=\frac{\sqrt{29}}{3}AB=329​​ so AB2=299AB^2=\frac{29}{9}AB2=929​

Hence, (t−4)2+(t−5)2=299(t-4)^2+(t-5)^2=\frac{29}{9}(t−4)2+(t−5)2=929​

Expand: t2−8t+16+t2−10t+25=299t^2-8t+16+t^2-10t+25=\frac{29}{9}t2−8t+16+t2−10t+25=929​ 2t2−18t+41=2992t^2-18t+41=\frac{29}{9}2t2−18t+41=929​

Multiply by 999: 18t2−162t+369=2918t^2-162t+369=2918t2−162t+369=29 18t2−162t+340=018t^2-162t+340=018t2−162t+340=0 9t2−81t+170=09t^2-81t+170=09t2−81t+170=0

Solve: t=81±812−4⋅9⋅17018t=\frac{81\pm\sqrt{81^2-4\cdot 9\cdot 170}}{18}t=1881±812−4⋅9⋅170​​ =81±6561−612018=\frac{81\pm\sqrt{6561-6120}}{18}=1881±6561−6120​​ =81±2118=\frac{81\pm 21}{18}=1881±21​

So, t=10218=173ort=6018=103t=\frac{102}{18}=\frac{17}{3} \quad \text{or} \quad t=\frac{60}{18}=\frac{10}{3}t=18102​=317​ort=1860​=310​

Thus possible points are: B1=(173,113),B2=(103,43)B_1=\left(\frac{17}{3},\frac{11}{3}\right), \qquad B_2=\left(\frac{10}{3},\frac{4}{3}\right)B1​=(317​,311​),B2​=(310​,34​)


  1. Use the slope condition

Slope of line through A(4,3)A(4,3)A(4,3) and BBB is m=yB−3xB−4m=\frac{y_B-3}{x_B-4}m=xB​−4yB​−3​

For B1=(173,113)B_1=\left(\frac{17}{3},\frac{11}{3}\right)B1​=(317​,311​):

m=\frac{\frac{11}{3}-3}{\frac{17}{3}-4}= rac{\frac{2}{3}}{\frac{5}{3}}=\frac{2}{5}<1 Not allowed.

For B2=(103,43)B_2=\left(\frac{10}{3},\frac{4}{3}\right)B2​=(310​,34​):

m=\frac{\frac{4}{3}-3}{\frac{10}{3}-4}= rac{-\frac{5}{3}}{-\frac{2}{3}}=\frac{5}{2}>1 Allowed.

So, B=(103,43)B=\left(\frac{10}{3},\frac{4}{3}\right)B=(310​,34​)


  1. Check the options

Option A: 2x+y=92x+y=92x+y=9

2⋅103+43=243=8≠92\cdot \frac{10}{3}+\frac{4}{3}=\frac{24}{3}=8\neq 92⋅310​+34​=324​=8=9 False.

Option B: 3x−2y=73x-2y=73x−2y=7

3⋅103−2⋅43=10−83=223≠73\cdot \frac{10}{3}-2\cdot \frac{4}{3}=10-\frac{8}{3}=\frac{22}{3}\neq 73⋅310​−2⋅34​=10−38​=322​=7 False.

Option C: x+2y=6x+2y=6x+2y=6

103+2⋅43=103+83=183=6\frac{10}{3}+2\cdot \frac{4}{3}=\frac{10}{3}+\frac{8}{3}=\frac{18}{3}=6310​+2⋅34​=310​+38​=318​=6 True.

Option D: 2x−3y=32x-3y=32x−3y=3

2⋅103−3⋅43=203−4=83≠32\cdot \frac{10}{3}-3\cdot \frac{4}{3}=\frac{20}{3}-4=\frac{8}{3}\neq 32⋅310​−3⋅34​=320​−4=38​=3 False.


  1. Final answer

The point BBB lies on x+2y=6\boxed{x+2y=6}x+2y=6​ So the correct option is C.

PreviousNext

More from Straight Lines and Pair of Straight Lines

  • Let the point P(α,β) be at a unit distance from each of the two lines L1​:3x−4y+12=0, and L2​:8x+6y+11=0. If P lies below L1​ and above L2​, then 100(α+β) is equal to :2022 · MCQ
  • A point P moves so that the sum of squares of its distances from the points (1,2) and (−2,1) is 14. Let f(x,y)=0 be the locus of P, which intersects the x-axis at the points A, B and the y-axis…2022 · MCQ
  • The equations of the sides AB,BC and CA of a triangle ABC are 2x+y=0,x+py=15a and x−y=3 respectively. If its orthocentre is (2,a),−21​<a<2, then…2022 · Numerical
  • Let R be the point (3, 7) and let P and Q be two points on the line x + y = 5 such that PQR is an equilateral triangle. Then the area of Δ PQR is :2022 · MCQ
  • Let A(1,1),B(−4,3),C(−2,−5) be vertices of a triangle ABC,P be a point on side BC, and Δ1​ and Δ2​ be the areas of triangles APB and ABC, respectively. If Δ1​:Δ2​=4:7, then the area…2022 · MCQ
  • The equations of the sides AB,BC and CA of a triangle ABC are 2x+y=0,x+py=39 and x−y=3 respectively and P(2,3) is its circumcentre. Then which of the following is NOT true?2022 · MCQ
  • In an isosceles triangle ABC, the vertex A is (6, 1) and the equation of the base BC is 2x + y = 4. Let the point B lie on the line x + 3y = 7. If (α, β) is the centroid of Δ ABC, then 15(α+β) is equal to :2022 · MCQ
  • A ray of light passing through the point P(2, 3) reflects on the x-axis at point A and the reflected ray passes through the point Q(5, 4). Let R be the point that divides the line segment AQ internally into the ratio 2 : 1. Let the…2022 · Numerical