The equation of a common tangent to the parabolas $y=x^{2}$ and $y=-(x-2)^{2}$ is
Solution
<p>Equation of tangent of slope $m$ to $y$ $= x^2$</p>
<p>$y = mx - {1 \over 4}{m^2}$</p>
<p>Equation of tangent of slope $m$ to $y = - {(x - 2)^2}$</p>
<p>$y = m(x - 2) + {1 \over 4}{m^2}$</p>
<p>If both equation represent the same line</p>
<p>${1 \over 4}{m^2} - 2m = - {1 \over 4}{m^2}$</p>
<p>$m = 0,\,4$</p>
<p>So, equation of tangent</p>
<p>$y = 4x - 4$</p>
About this question
Subject: Mathematics · Chapter: Conic Sections · Topic: Parabola
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