Medium MCQ +4 / -1 PYQ · JEE Mains 2021

If the curve y = ax2 + bx + c, x$\in$R, passes through the point (1, 2) and the tangent line to this curve at origin is y = x, then the possible values of a, b, c are :

  1. A a = $-$ 1, b = 1, c = 1
  2. B a = 1, b = 1, c = 0 Correct answer
  3. C a = ${1 \over 2}$, b = ${1 \over 2}$, c = 1
  4. D a = 1, b = 0, c = 1

Solution

Given curve y = ax<sup>2</sup> + bx + c, x$\in$R <br><br>This curve passes through the point (1, 2) <br><br>$\therefore$ $2 = a + b + c$ ..... (i) <br><br>Given, slope of tangent at origin is 1 <br><br>$\therefore$ $${{dy} \over {dx}} = 2ax + b \Rightarrow {\left. {{{dy} \over {dx}}} \right|_{(0,0)}} = 1$$<br><br>$\Rightarrow b = 1 \Rightarrow a + c = 1$<br><br>(0, 0) lie on curve<br><br>$\therefore$ c = 0, a = 1

About this question

Subject: Mathematics · Chapter: Application of Derivatives · Topic: Tangents and Normals

This question is part of PrepWiser's free JEE Main question bank. 99 more solved questions on Application of Derivatives are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →