Browse Questions

# Choose the correct answer from the given four options. The equation of the line passing through the point (1, 2) and perpendicular to the line $x+y+1 = 0$ is

$\begin {array} {1 1} (A)\;y – x + 1 = 0 & \quad (B)\;y – x – 1 = 0 \\ (C)\;y – x + 2 = 0 & \quad (D)\;y – x – 2 = 0 \end {array}$

Toolbox:
• The slope of a line perpendicular to a given line where slope is $'m'$ is $- \large\frac{1}{m}$.
Step 1 :
Equation of the given line is
$x+y+1=0$
Slope of this line is -1.
Equation of the required line which is perpendicular to the above line is
$x-y+k=0$
This line passes through the point (1,2)
$\therefore 1-2+k=0$
$\Rightarrow k-1=0$ or $k=1$
Hence equation of the required line is
$x-y+1=0$
Hence B is the correct option.