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JEE Main 202227 JulyMorning Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Morning Shift
Subject
Mathematics
Chapter
Straight Lines

JEE Main 2022 · 27 July · Morning Shift · Mathematics · Straight Lines

Let A (1, 1), B (- 4, 3), C(- 2, - 5) be vertices of a triangle...

Let AA\left(1, 1\right), B(−4,3),C(−2,−5)\left(- 4, 3\right), C\left(- 2, - 5\right) be vertices of a triangle ABC,PABC, P be a point on side BCBC, and Δ1{\Delta}_{1} and Δ2{\Delta}_{2} be the areas of triangle APBAPB and ABCABC.

Respectively.

If Δ1:Δ2=4:7{\Delta}_{1}: {\Delta}_{2} = 4: 7, then the area enclosed by the lines AP,ACAP, AC and the xx-axis is

Let A (1, 1), B (- 4, 3), C(- 2, - 5) be vertices of a triangle ABC, P be a point on side BC , and Δ _ 1 and Δ _ 2 be

Options

  1. A14\dfrac{1}{4}
  2. B34\dfrac{3}{4}
  3. C12\dfrac{1}{2}
  4. D11

Correct answer

C. 12\dfrac{1}{2}

Step-by-step solution

Plotting the given value in diagram we have,

Let A (1, 1), B (- 4, 3), C(- 2, - 5) be vertices of a triangle ABC, P be a point on side BC , and Δ _ 1 and Δ _ 2 be

Now let P(x,y)P\left(x, y\right) be a point on BCBC, so area formed by △ABP△ ABP will be,

{\Delta}_{1} = \dfrac{1}{2}\left|\begin{cases}x & y & 1 \\ 1 & 1 & 1 \\ - 4 & 3 & 1\end{cases}\right| = \dfrac{1}{2}\left(- 2x - 5y + 7\right)

And area of triangle formed by △ABC△ ABC will be, {\Delta}_{2} = \dfrac{1}{2}\left|\begin{cases}1 & 1 & 1 \\ - 4 & 3 & 1 \\ - 2 & - 5 & 1\end{cases}\right| = \dfrac{36}{2}

Given Δ1Δ2=47⇒−2x−5y+736=47\dfrac{{\Delta}_{1}}{{\Delta}_{2}} = \dfrac{4}{7} ⇒ \dfrac{- 2x - 5y + 7}{36} = \dfrac{4}{7}

⇒14x+35y=−95⋯(1)⇒ 14x + 35y = - 95 ⋯ \left(1\right)

Equation of BCBC by two point form will be 4x+y=−13⋯(2)4x + y = - 13 ⋯ \left(2\right)

Solving equation \left(1\right)and(2)and \left(2\right) we get,

Point P(−207,−117)P\left(\dfrac{- 20}{7}, \dfrac{- 11}{7}\right)

Now equation of APAP will be y−1=1+1171+207(x−1)y - 1 = \dfrac{1 + \dfrac{11}{7}}{1 + \dfrac{20}{7}}\left(x - 1\right)

⇒3y−2x=1⇒ 3y - 2x = 1,

So x−x -intercept will be point Q(−12,0)Q\left(\dfrac{- 1}{2}, 0\right) and similarly from ACAC we get R(12,0)R\left(\dfrac{1}{2}, 0\right)

So Area of triangle AQR=12×1×1=12AQR = \dfrac{1}{2} \times 1 \times 1 = \dfrac{1}{2}

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