The centroid of the triangle formed by the pair of straight lines $12 x^2-20 x y+7 y^2=0$ and the line $2…

The centroid of the triangle formed by the pair of straight lines $12 x^2-20 x y+7 y^2=0$ and the line $2 x-3 y+4=0$ is :
  1. $\left(-\frac{7}{3}, \frac{7}{3}\right)$
  2. $\left(-\frac{8}{3}, \frac{8}{3}\right)$
  3. $\left(\frac{8}{3}, \frac{8}{3}\right)$
  4. $\left(\frac{4}{3}, \frac{4}{3}\right)$

Solution

The separate equation of pair of straight lines of $12 x^2-20 x y+7 y^2=0$ are $(6 x-7 y)=0$ and $(2 x-y)=0$ These the equation of sides are $6 x-7 y=0$ $\ldots$ (i) $2 x-y=0$ $\ldots$ (ii) and $2 x-3 y+4=0$ $\ldots$ (iii) On solving these equations, taking two at a time we get the vertices of a triangle which are $A(0,0) ; B(1,2)$ and $(7,6)$ $\therefore$ Centroid of a triangle is $\left(\frac{0+1+7}{3}, \frac{0+2+6}{3}\right)$ i.e., $\quad\left(\frac{8}{3}, \frac{8}{3}\right)$

Asked in: AP EAMCET 2006

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