Question

Write and equati9n of a l8ne that passes through (1,-2) and is perpendicular to -4x+7y=21

Answer 1

Given:

A line passes through (1,-2) and is perpendicular to $-4x+7y=21$.

To find:

The equation of that line.

Solution:

We have, equation of perpendicular line.

$-4x+7y=21$

Slope of this line is

$m_1=-\dfrac{\text{Coefficient of x}}{\text{Coefficient of y}}$

$m_1=-\dfrac{-4}{7}$

$m_1=\dfrac{4}{7}$

Product of slope of two perpendicular lines is -1.

$m_1\times m_2=-1$

$\dfrac{4}{7}\times m_2=-1$

$m_2=-\dfrac{7}{4}$

Now, slope of required line is $-\dfrac{7}{4}$ and it passes through (1,-2). So, the equation of line is

$y-y_1=m(x-x_1)$

where, m is slope.

$y-(-2)=-\dfrac{7}{4}(x-1)$

$4(y+2)=-7(x-1)$

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

$4y+7x=7-8$

$7x+4y=-1$

Therefore, the equation of required line is $7x+4y=-1$.