Question

prove algebraically that the straight line with equation x = 2y + 5 is a tangent to the circle with equation x^2 + y^2 = 5

Answer 1

Explanation:

Find the point(s) of intersection

(2y+5)^2 + y^2 = 5

5 y^2 + 20 y + 20 = 0 Quadratic formula shows y = -2 only.....so the line only touches at ONE point and is thus tangential .