Continuity and Differentiability — Class 12 Maths Solution

exemplar objective MCQ NCERT Exemp. Ex.5.3 ,Q.94,Page 115
Question

If $x = {t^2}$ and $y = {t^3},$ then $\frac{{{d^2}y}}{{d{x^2}}}$ is equal to

  • (a) $\frac{3}{2}$
  • (b) $\frac{3}{{4t}}$ ✓ Correct
  • (c) $\frac{3}{{2t}}$
  • (d) $\frac{3}{{2t}}$
Step-by-step Solution
Correct answer: option (b)

We have, $x = {t^2}$ and $y = {t^3}$

therefore,$\frac{{dx}}{{dt}} = 2t$ and $\frac{{dy}}{{dt}} = 3{t^2}$
therefore,$\frac{{dy}}{{dx}} = \frac{{dy/dt}}{{dx/dt}} = \frac{{3{t^2}}}{{2t}} = \frac{3}{2}t$

On further differentiating w.r.t. $x$, we get
$\frac{{{d^2}y}}{{d{x^2}}} = \frac{3}{2} \cdot \frac{d}{{dt}}t \cdot \frac{{dt}}{{dx}}$

$= \frac{3}{2} \cdot \frac{1}{{2t}}$

$= \frac{3}{{4t}}$

NCERT & Exemplar solution for CBSE Class 12 Mathematics, Continuity and Differentiability. Curated by Sachin Sharma. Free for all students.