11. (a) Let $\mathrm { a } , \mathrm { b } , \mathrm { c }$ be real numbers with $\mathrm { a } ^ { 1 } 0$ and let $\mathrm { a } , \mathrm { b }$ be the roots of the equation $\mathrm { ax } 2 + \mathrm { bx } + \mathrm { c } = 0$. Express the roots of $\mathrm { a } 2 \times 2 + \mathrm { abcx } + \mathrm { c } 3 = 0$ in terms of $\mathrm { a } , \mathrm { b }$.
(b) Let $\mathrm { a } , \mathrm { b } , \mathrm { c }$ be real numbers with $\mathrm { a } 2 + \mathrm { b } 2 + \mathrm { c } 2 = 1$. Show that the equation
$$\left| \begin{array} { c c c }
a x - b y - c & b x + a y & c x + a \\
b x + a y & - a x + b y - c & c y + b \\
c x + a & c y + b & - a x - b y + c
\end{array} \right| = 0 \text { represents a straight line. }$$
- (a) Let P be a point on the ellipse $\mathrm { x } 2 / \mathrm { a } 2 + \mathrm { y } 2 / \mathrm { b } 2 = 1,0 < \mathrm { b } < \mathrm { a }$. Let the line parallel to-qxis passing through P meet the circle $\mathrm { x } 2 + \mathrm { y } 2 = \mathrm { a } 2$ at the point Q such that P and Q are on the same side of - xxis . For two positive real numbers r and s , find the locus of the point R on PQ such that $\mathrm { PR } : \mathrm { RQ } = \mathrm { r } : \mathrm { s }$ as P varies over the ellipse.
(b) If D is the area of a triangle with side lengths $\mathrm { a } , \mathrm { b } , \mathrm { c }$ then show that $\mathrm { D } < 1 / 4 \sqrt { } ( ( \mathrm { a } + \mathrm { b } + \mathrm { c } ) \mathrm { abc } )$.
Also show that the equality occurs in the above inequality if and only if $\mathrm { a } = \mathrm { b } = \mathrm { c }$.