Question

Find the value of k if the line 2x-y+k=0 may touch the circle x^2 + y^2=5​

Answer 1

k = ±4

Explanation:

Equation of the circle is:

x² + y² = 5​

This means from the general form of equation of a circle;

Centre coordinates is (0, 0) and radius is; √5.

The line 2x - y + k = 0 touches the circle. Thus, perpendicular distance from centre of the circle to this line is equal to the circle radius;

Thus;

|((2 - 0) - (1 × 0) + k)|/(√(2² + 1²)) = √5

|(1 + k)|/√5 = √5

Multiply both sides by √5 to get;

|1 + k| = 5

|k| = 5 - 1

k = ±4