Write an equation of the line containing the given point and parallel to the given line. Let us consider that the given point is (1, 2) and the line is x + y = 1.

We will use the concept of straight lines in order to find the equation of the line.

Answer: y = -x + 3 is the equation of our required line.

Let us see how we will use the concept of straight lines in order to find the equation of the line.

Explanation:

For the line x + y = 1. This line can also be written as y = 1 - x.

Hence, the slope of the line y = 1 - x is -1.

Since our required line is parallel to the line x + y = 1, hence the slope of our required line is also -1.

Now let us consider that our required line also passes through the point (x, y).

From the definition of slope we can also write,

(y - 2) / (x - 1) = -1

⇒ y - 2 = -x + 1

⇒ y = -x + 3

Hence, y = -x + 3 is the equation of our required line.