The equation of a straight line passing through (1, 2) and perpendicular to $$x + y + 1 = 0$$​ is:

Correct option is C

Given:
Point (x₁, y₁) = (1, 2)
Given line: x + y + 1 = 0
Formula used:
If ax + by + c = 0, slope $$m = −a/b$$​​
Slope of a line perpendicular to it is the negative reciprocal.
Solution:
For x + y + 1 = 0:
Slope $$m₁ = −1$$​​
So slope of required line:
​$$m₂ = 1$$​​
Equation of line with slope 1 passing through (1, 2):
​$$y − 2 = 1(x − 1)\\y − 2 = x − 1\\y − x − 1 = 0$$​​
The correct answer is (c) y − x − 1 = 0.