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Find the point on the axis of the parabo...

Find the point on the axis of the parabola `3y^2+4y-6x+8 =0` from where three distinct normals can be drawn.

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To find the point on the axis of the parabola \(3y^2 + 4y - 6x + 8 = 0\) from where three distinct normals can be drawn, we will follow these steps: ### Step 1: Rewrite the equation in standard form We start with the given equation: \[ 3y^2 + 4y - 6x + 8 = 0 \] Rearranging gives: \[ 3y^2 + 4y = 6x - 8 \] Now, we factor out the 3 from the left side: \[ 3(y^2 + \frac{4}{3}y) = 6x - 8 \] Next, we complete the square for the \(y\) terms. The coefficient of \(y\) is \(\frac{4}{3}\). Half of this is \(\frac{2}{3}\), and squaring it gives \(\frac{4}{9}\). We add and subtract this inside the bracket: \[ 3\left(y^2 + \frac{4}{3}y + \frac{4}{9} - \frac{4}{9}\right) = 6x - 8 \] This simplifies to: \[ 3\left((y + \frac{2}{3})^2 - \frac{4}{9}\right) = 6x - 8 \] Distributing the 3 gives: \[ 3(y + \frac{2}{3})^2 - \frac{4}{3} = 6x - 8 \] Now, adding \(\frac{4}{3}\) to both sides: \[ 3(y + \frac{2}{3})^2 = 6x - 8 + \frac{4}{3} \] Converting \(-8\) to a fraction with a denominator of 3 gives \(-\frac{24}{3}\): \[ 3(y + \frac{2}{3})^2 = 6x - \frac{24}{3} + \frac{4}{3} \] This simplifies to: \[ 3(y + \frac{2}{3})^2 = 6x - \frac{20}{3} \] Dividing everything by 3: \[ (y + \frac{2}{3})^2 = 2x - \frac{20}{9} \] This is now in the standard form of a parabola. ### Step 2: Identify the vertex and axis of the parabola From the standard form \((y - k)^2 = 4p(x - h)\), we can identify: - Vertex \((h, k) = \left(\frac{10}{9}, -\frac{2}{3}\right)\) - The axis of the parabola is given by \(y = -\frac{2}{3}\). ### Step 3: Determine the conditions for three distinct normals For three distinct normals to be drawn from a point on the axis, the condition is: \[ h > 2a \] where \(a\) is the distance from the vertex to the focus. From the standard form, we have \(4p = 2\), thus \(p = \frac{1}{2}\) and \(a = \frac{1}{2}\). ### Step 4: Substitute and solve the inequality Substituting \(a\) into the inequality: \[ h > 2 \times \frac{1}{2} \implies h > 1 \] The x-coordinate \(h\) of any point on the axis is given by: \[ h = x - \frac{10}{9} \] Thus: \[ x - \frac{10}{9} > 1 \implies x > 1 + \frac{10}{9} = \frac{19}{9} \] ### Step 5: Identify the point on the axis The y-coordinate of any point on the axis is fixed at: \[ y = -\frac{2}{3} \] Thus, the point on the axis from where three distinct normals can be drawn is: \[ \left(h, -\frac{2}{3}\right) \text{ where } h > \frac{19}{9} \] So, we can choose any \(h\) greater than \(\frac{19}{9}\), for example, \(h = \frac{20}{9}\). ### Final Answer The point on the axis of the parabola from where three distinct normals can be drawn is: \[ \left(\frac{20}{9}, -\frac{2}{3}\right) \]
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ARIHANT MATHS ENGLISH-PARABOLA-Exercise (Questions Asked In Previous 13 Years Exam)
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  3. Let P be the point (1,0) and Q be a point on the locus y^(2)=8x. The l...

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  4. The axis of a parabola is along the line y=x and the distance of its v...

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  6. The locus of the vertex of the family of parabolas y=(a^3x^2)/3+(a^(2x...

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  7. The angle between the tangents to the curve y=x^2-5x+6 at the point (2...

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  8. Consider the circle x^2 + y^2 = 9 and the parabola y^2 = 8x. They inte...

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  9. Consider the circle x^2 + y^2 = 9 and the parabola y^2 = 8x. They inte...

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  10. Find slope of tangent to the curve if equation is x^2 + y^2 = 9

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  11. Statement 1 : The curve y=-(x^2)/2+x+1 is symmetric with respect to th...

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  12. The equation of a tangent to the parabola y^2=""8x""i s""y""=""x""+...

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  13. Consider two curves C1:y^2=4x ; C2=x^2+y^2-6x+1=0. Then, a. C1 and C2 ...

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  14. If a parabola has the origin as its focus and the line x = 2 as the ...

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  16. Let A and B be two distinct points on the parabola y^2=4x. If the ax...

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  17. If two tangents drawn from a point P to the parabola y2 = 4x are at ri...

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