- Exam
- JEE Main
- Year
- 2022
- Date
- 27 July
- Shift
- Evening Shift
- Subject
- Mathematics
- Chapter
- Continuity and Differentiability
JEE Main 2022 · 27 July · Evening Shift · Mathematics · Continuity and Differentiability
If for p ≠ q ≠ 0 , then function f(x) = (p(729 + x)7 - 3)/(729 +...
Options
- A
- B
- C
- D
Correct answer
B.
Step-by-step solution
For a function to be continuous \left(x\right)x = 0f\left(0\right) = \lim_{x \to 0}f\left(x\right)f\left(x\right) = \dfrac{p\left(729 + x\right)7 - 3}{729 + qx3 - 9}\dfrac{0}{0}\lim_{x \to 0}\left(p\left(729 + x\right)7 - 3\right)p . 7297 - 3 = 0⇒ p \cdot 729 = {3}^{7} ⇒ p = 3f\left(0\right) = \lim_{x \to 0}\dfrac{3\left({3}^{6} + x\right)7 - 3}{{3}^{6} + qx3 - 9}= \lim_{x \to 0}\dfrac{3\left[{\left(1 + \dfrac{x}{{3}^{6}}\right)}^{\dfrac{1}{7}} - 1\right]}{9\left[{\left(1 + \dfrac{qx}{{3}^{6}}\right)}^{\dfrac{1}{3}} - 1\right]} = \dfrac{3}{9} \times \dfrac{\dfrac{1}{7 \cdot {3}^{6}}}{\dfrac{q}{3 \cdot {3}^{6}}}⇒ f\left(0\right) = \dfrac{1}{3} \times \dfrac{3}{7q} = \dfrac{1}{7q}⇒ 7qf\left(0\right) - 1 = 0⇒ 7 \cdot {p}^{2} \cdot qf\left(0\right) - {p}^{2} = 0{p}^{2}⇒ 63qf\left(0\right) - {p}^{2} = 0