Question

Find the equation of the line that passes through the point of intersection of x + 2y = 9 and 4x -2y = -4 and the point of intersection of intersection of the lines 3x - 4y = 14 and 3x + 7y = -8.

Answer 1

Answer:

$y=-6x+10$

Step-by-step explanation:

The point of intersection of

$x+2y=9...eqn1$

and

$4x-2y=-4...eqn2$

is the solution of the two equations.

We add equation (1) and equation(2) to get,

$x+4x+2y-2y=9+-4$

$\Rightarrow 5x=5$

$\Rightarrow x=1$

We put $x=1$ into equation (1) to get,

$1+2y=9$

$\Rightarrow 2y=9-1$

$\Rightarrow 2y=8$

$\Rightarrow y=4$

Therefore the line passes through the point, $(1,4)$.

The line also passes through the point of intersection of

$3x-4y=14...eqn(3)$

and

$3x+7y=-8...eqn(4)$

We subtract equation (3) from equation (4) to obtain,

$3x-3x+7y--4y=-8-14$

$\Rightarrow 11y=-22$

$\Rightarrow y=-2$

We substitute this value into equation (4) to get,

$3x+7(-2)=-8$

$3x-14=-8$

$3x=-8+14$

$3x=6$

$x=2$

The line also passes through

$(2,-2)$

The slope of the line is

$slope=\frac{4--2}{1-2} =\frac{6}{-1}=-6$

The equation of the line is

$y+2=-6(x-2)$

$y+2=-6x+12$

$y=-6x+10$ is the required equation