Verified Solution • 2025–26 Session moderate

QJEEM24Maed04: JEE Main 2024 Mathematics - Class 11 JEEM24Maed04 Solution: Let be the interior region between the lines and containing the …

Let R\mathrm{R} be the interior region between the lines 3x−y+1=03 x-y+1=0 and x+2y−5=0x+2 y-5=0 containing the origin. The set of all values of aa , for which the points (a2,a+1)\left(a^2, a+1\right) lie in RR , is :

Multiple Choice Options

  • A (−3,0)∪(23,1)(-3,0) \cup\left(\frac{2}{3}, 1\right)
  • B (−3,0)∪(13,1)(-3,0) \cup\left(\frac{1}{3}, 1\right)
  • C (−3,−1)∪(13,1)(-3,-1) \cup\left(\frac{1}{3}, 1\right)
  • D (−3,−1)∪(−13,1)(-3,-1) \cup\left(-\frac{1}{3}, 1\right)

Step-by-Step Verified Solution

amp;P(a2,a+1)amp;L1=3x−y+1=0\begin{aligned}& \mathrm{P}\left(\mathrm{a}^2, \mathrm{a}+1\right) \\& \mathrm{L}_1=3 \mathrm{x}-\mathrm{y}+1=0\end{aligned}

Origin and P\mathrm{P} lies same side w.r.t. L1\mathrm{L}_1

amp;⇒L1(0)⋅L1(P)gt;0amp;∴3(a2)−(a+1)+1gt;0\begin{aligned}& \Rightarrow \mathrm{L}_1(0) \cdot \mathrm{L}_1(\mathrm{P})>0 \\& \therefore 3\left(\mathrm{a}^2\right)-(\mathrm{a}+1)+1>0\end{aligned}

JEE Main 2024 (Online) 27th January Evening Shift Mathematics - Straight Lines and Pair of Straight Lines Question 30 English Explanation

amp;⇒3a2−agt;0amp;a∈(−∞,0)∪(13,∞)..... (1)\begin{aligned}& \Rightarrow 3 \mathrm{a}^2-\mathrm{a}>0 \\& \mathrm{a} \in(-\infty, 0) \cup\left(\frac{1}{3}, \infty\right) \quad \text{..... (1)}\end{aligned}

Let L2:x+2y−5=0L_2: x+2 y-5=0

Origin and P\mathrm{P} lies same side w.r.t. L2\mathrm{L}_2

amp;⇒L2(0)⋅L2(P)gt;0amp;⇒a2+2(a+1)−5lt;0amp;⇒a2+2a−3lt;0amp;⇒(a+3)(a−1)lt;0\begin{aligned}& \Rightarrow \mathrm{L}_2(0) \cdot \mathrm{L}_2(\mathrm{P})>0 \\& \Rightarrow \mathrm{a}^2+2(\mathrm{a}+1)-5<0 \\& \Rightarrow \mathrm{a}^2+2 \mathrm{a}-3<0 \\& \Rightarrow(\mathrm{a}+3)(\mathrm{a}-1)<0\end{aligned}

∴a∈(−3,1)..... (2)\therefore \mathrm{a} \in(-3,1)\quad \text{..... (2)}

Intersection of (1) and (2)

a∈(−3,0)∪(13,1)\mathrm{a} \in(-3,0) \cup\left(\frac{1}{3}, 1\right)

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