CBSE Class 12 Sample Paper for 2022 Boards (MCQ Based - for Term 1)

Class 12
Solutions of Sample Papers and Past Year Papers - for Class 12 Boards

## (c) 2Β  Β  Β  Β (d) 3

Β

This question is inspired from Misc 21 (MCQ) - Chapter 6 Class 12 - Application of Derivatives

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### Transcript

Question 42 For which value of m is the line y = mx + 1 a tangent to the curve y2 = 4x? (a) 1/2 (b) 1 (c) 2 (d) 3 Let (β , π) be the point at which tangent is to be taken Since (π , π) lies on line π=πβ+1 Since (π , π) lies on curve π^2=4β β=π^2/4 Putting (2) in (1) π=π(π^π/π)+1 4π=ππ^2+4 ππ^2β4π+4=0 Since tangent touches the curve at only one point There is only one value of k So, this quadratic equation has only one root Thus, Discriminant of Quadratic equation = 0 π^πβπππ=π (β4)^2β4 Γ π Γ 4=0 16β16π=0 π=16/16 π=π So, the correct answer is (B)