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Derive the conditions to be imposed on \beta so that \mathrm{(0, \beta)} should lie inside the triangle having sides \mathrm{y+3 x+2=0,3 y-2 x-5=0 \; and \; 4 y+x-14=0}

Option: 1

\mathrm{\frac{-5}{2}<\beta <\frac{-3}{2}}


Option: 2

\mathrm{\frac{5}{3}<\beta <\frac{7}{2}}


Option: 3

\mathrm{\frac{5}{2}<\beta <\frac{7}{2}}


Option: 4

\mathrm{5<\beta <7}


Answers (1)

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Let  the  equation  of BC be

\mathrm{4 y+x-14=0}\: \: \: \: \: \: \: \: \: \: \: \: \: ....(1)

Equation  of CA  be

\mathrm{y + 3x+ 2 = 0}\: \: \: \: \: \: \: \: \: \: \: \: \: ....(2)

And equation of AB be

\mathrm{3y - 2x - 5 = 0}\: \: \: \: \: \: \: \: \: \: \: \: \: ....(3)

Let \mathrm{P \equiv(0, \beta)}

Solving  these  equations two by two,  we get

\mathrm{A \equiv(-1,1), B \equiv(2,3) \text { and } C \equiv(-2,4) \text {. }}

For point \mathrm{\mathrm{A}(-1,1), 4 \mathrm{y}+\mathrm{x}-14=-11<0}

For point \mathrm{P(0, \beta), 4 y+x-14=4 \beta-14}

For point \mathrm{{B}(2,3), y+3 x+2=3+6+2=11>0}

For point \mathrm{P(0, \beta), y+3 x+2=\beta+2}

For point \mathrm{C(-2,4), 3 y-2 x-5=11>0}

For point \mathrm{P(0, \beta), 3 y-2 x-5=3 \beta-5}

Point \mathrm{P(0, \beta)} will lie inside \mathrm{\triangle \mathrm{ABC}} only when P, A lie on the same side of BC, P, B lie on the same side of AC and P, C lie  on the  same  side of AB  i.e.  only  when 

\mathrm{4\beta -14 <0\Rightarrow \beta \frac{7}{2}}\; \; \; \; \; \; \; \; \; \; \; \; ...(4)

\mathrm{\beta+2>0 \Rightarrow \beta>-2}\; \; \; \; \; \; \; \; \; \; \; \; ...(5)

and \mathrm{3 \beta-5>0 \Rightarrow \beta>\frac{5}{3}}\; \; \; \; \; \; \; \; \; \; \; \; ...(6)

From (4), (5) and  (6),  we have  \mathrm{\frac{5}{3}<\beta<\frac{7}{2}}

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