- Home
- Standard 11
- Mathematics
9.Straight Line
normal
Two consecutive sides of a parallelogram are $4x + 5y = 0$ and $7x + 2y = 0$. If the equation to one diagonal is $11x + 7y = 9$, then the equation to the other diagonal is :-
A
$3x + 7y = 0$
B
$11x -7y = 0$
C
$x -y = 0$
D
$x + y = 0$
Solution

$4 x+5 y=0$ ……$(i)$
$7 x+2 y=0$ ……..$(ii)$
$11 x+7 y=9$ ……..$(iii)$
Solving $(i)$ and $(iii)$
$A \equiv \left( {\frac{5}{3}, – \frac{4}{3}} \right)$
Solving $(ii)$ and $(iii)$
$C \equiv\left(-\frac{2}{3}, \frac{7}{3}\right)$
Co-ordinates of middle point of $\mathrm{AC}$
$M \equiv \left( {\frac{1}{2},\frac{1}{2}} \right)$
Equation of other diagonal which passes through $\mathrm{O}$ and $\mathrm{M}$ is
$y-0=\frac{\frac{1}{2}-0}{\frac{1}{2}-0}(x-0)$
or $y=x$
Standard 11
Mathematics