Question

The line y = mx + 1 is a tangent to the curve y² = 4x if the value of m is

(A)   1    (B)   2      (C)    3     (D)     1/2

Answer 1

The equation of the tangent to the given curve is y = mx + 1.
Now, substituting y = mx + 1 in y² = 4x, we get:

Since a tangent touches the curve at one point, the roots of equation (i) must be equal.
Therefore, we have:

Hence, the required value of m is 1.
The correct answer is A.