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

2020 · 3 Sep · Shift 2 · Q35
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. /2020 · 3 Sep · Shift 2 · Q35

Straight Lines and Pair of Straight Lines question

2020 · 3 Sep · Shift 2 · Q35

JEE MainMathematicsStraight Lines and Pair of Straight LinesMCQ+4 / −1
If a Δ\DeltaΔ ABC has vertices A(–1, 7), B(–7, 1) and C(5, –5), then its orthocentre has coordinates :
  1. A
    (–3, 3)
  2. B
    (3, –3)
  3. C
    (35,−35)\left( {{3 \over 5}, - {3 \over 5}} \right)(53​,−53​)
  4. D
    (−35,35)\left( { - {3 \over 5},{3 \over 5}} \right)(−53​,53​)
View written solutionFree

Correct answer: A

  1. Given vertices

A(−1,7),B(−7,1),C(5,−5)A(-1,7),\quad B(-7,1),\quad C(5,-5)A(−1,7),B(−7,1),C(5,−5)

We need the orthocentre, i.e. the point of intersection of the altitudes.


  1. Find slope of side BCBCBC

Points B(−7,1)B(-7,1)B(−7,1) and C(5,−5)C(5,-5)C(5,−5) give

mBC=−5−15−(−7)=−612=−12m_{BC}=\frac{-5-1}{5-(-7)}=\frac{-6}{12}=-\frac12mBC​=5−(−7)−5−1​=12−6​=−21​

So the altitude from AAA is perpendicular to BCBCBC, hence its slope is

mA-alt=2m_{A\text{-alt}}=2mA-alt​=2

Equation of altitude through A(−1,7)A(-1,7)A(−1,7):

y−7=2(x+1)y-7=2(x+1)y−7=2(x+1) y=2x+9y=2x+9y=2x+9


  1. Find slope of side ACACAC

Points A(−1,7)A(-1,7)A(−1,7) and C(5,−5)C(5,-5)C(5,−5) give

mAC=−5−75−(−1)=−126=−2m_{AC}=\frac{-5-7}{5-(-1)}=\frac{-12}{6}=-2mAC​=5−(−1)−5−7​=6−12​=−2

So the altitude from BBB is perpendicular to ACACAC, hence its slope is

mB-alt=12m_{B\text{-alt}}=\frac12mB-alt​=21​

Equation of altitude through B(−7,1)B(-7,1)B(−7,1):

y−1=12(x+7)y-1=\frac12(x+7)y−1=21​(x+7)

2y−2=x+72y-2=x+72y−2=x+7 x−2y+9=0x-2y+9=0x−2y+9=0

or

y=12x+92y=\frac12x+\frac92y=21​x+29​


  1. Find intersection of the two altitudes

Solve

y=2x+9y=2x+9y=2x+9 y=12x+92y=\frac12x+\frac92y=21​x+29​

Equating,

2x+9=12x+922x+9=\frac12x+\frac922x+9=21​x+29​

Multiply by 222:

4x+18=x+94x+18=x+94x+18=x+9 3x=−93x=-93x=−9 x=−3x=-3x=−3

Then

y=2(−3)+9=3y=2(-3)+9=3y=2(−3)+9=3

So the orthocentre is

(−3,3)(-3,3)(−3,3)


  1. Check with options

Option A: (−3,3)(-3,3)(−3,3) ✅

Hence the correct answer is A.


  1. Comparison with stored answer

Stored correct answer: A

Our derived answer: A

They match.

PreviousNext

More from Straight Lines and Pair of Straight Lines

  • Two vertical poles AB = 15 m and CD = 10 m are standing apart on a horizontal ground with points A and C on the ground. If P is the point of intersection of BC and AD, then the height of P (in m) above the line AC is :2020 · MCQ
  • If the perpendicular bisector of the line segment joining the points P(1 ,4) and Q(k, 3) has y-intercept equal to –4, then a value of k is :2020 · MCQ
  • If the line, 2x - y + 3 = 0 is at a distance 5​1​ and 5​2​ from the lines 4x - 2y +α= 0 and 6x - 3y +β= 0, respectively, then the sum of all possible values of α and β is :2020 · Numerical
  • A ray of light coming from the point (2, 23​) is incident at an angle 30o on the line x = 1 at the point A. The ray gets reflected on the line x = 1 and meets x-axis at the point B. Then, the line AB passes through the point :2020 · MCQ
  • Let L denote the line in the xy-plane with x and y intercepts as 3 and 1 respectively. Then the image of the point (–1, –4) in this line is :2020 · MCQ
  • Let A(1, 0), B(6, 2) and C (23​,6) be the vertices of a triangle ABC. If P is a Point inside the triangle ABC such that the triangles APC, APB and BPC have equal areas, then the length of the line segment PQ,…2020 · Numerical
  • The locus of the mid-points of the perpendiculars drawn from points on the line, x = 2y to the line x = y is :2020 · MCQ
  • Let two points be A(1, –1) and B(0, 2). If a point P(x', y') be such that the area of Δ PAB = 5 sq. units and it lies on the line, 3x + y – 4 λ= 0, then a value of λ is :2020 · MCQ