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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Mathematics
Chapter
Area Under Curves

NTA Abhyas 2020 · Mathematics · Area Under Curves

The area enclosed between the curves y = ax ^ 2 and x = ay ^ 2 (a >...

The area enclosed between the curves y=ax2and\text{y} = {\text{ax}}^{2} and\text{x} = {\text{ay}}^{2} (a>0)\left(\text{a} > 0\right) is 11 sq unit. If the value of aa is 33λ\dfrac{3\sqrt{3}}{\lambda}, then the value of λ\lambda isThe area enclosed between the curves y = ax ^ 2 and x = ay ^ 2 (a > 0) is 1 sq unit. If the value of a is 3 3 λ , then

Correct answer

9

Step-by-step solution

As from the figure, area enclosed between the curves is OABCOOABCO.

Thus, the points of intersection of

y=ax2and\text{y} = {\text{ax}}^{2} and\text{x} = {\text{ay}}^{2},<br/>eliminating,<br />eliminatingy,weget<br/><br/>, we get<br /><br />x = a{( {ax}^{2} )}^{2}<br/><br/><br /><br />⇒ x - {a}^{3}{x}^{4} = 0<br/><br/><br /><br />⇒ x( 1 - {a}^{3}{x}^{3} ) = 6<br/><br/><br /><br />⇒ x = 0\text{and}x = \dfrac{1}{a}<br/><br/><imgalt=""src="https://cdn−question−pool.getmarks.app/ntaabhyas/jeemain/images/math−3.png"/><br/><br/><br /><br /><img alt="" src="https://cdn-question-pool.Quantrex.app/nta_abhyas/jee_main/images/math-3.png" /><br /><br />∴PointsofintersectionarePoints of intersection are( 0, 0 )and(1a,1a)and \left(\dfrac{1}{\text{a}} \text{,} \dfrac{1}{\text{a}}\right).

Thus, required area OABCOOABCO = Area of curve OCBDOOCBDO - area of curve OABDOOABDO

⇒⇒ ∫01/a(xa−ax2)dx=1{∫}_{0}^{1 / \text{a}} \left(\sqrt{\dfrac{\text{x}}{\text{a}}} - {\text{ax}}^{2}\right) \text{dx} = 1 (given)

⇒⇒ [1a⋅⋅x3/23/2−ax33]01/a=1{\left[\dfrac{1}{\sqrt{\text{a}} \cdot} \cdot \dfrac{{\text{x}}^{3 / 2}}{3 / 2} - \dfrac{{\text{ax}}^{3}}{3}\right]}_{0}^{1 / \text{a}} = 1

⇒⇒ 23a2−13a2=1\dfrac{2}{3 {\text{a}}^{2}} - \dfrac{1}{3 {\text{a}}^{2}} = 1

⇒a2=13⇒a=13(∵a>0)⇒ {\text{a}}^{2} = \dfrac{1}{3} ⇒ \text{a} = \dfrac{1}{\sqrt{3}} ( ∵ \text{a} > 0 )

13=33λ\dfrac{1}{\sqrt{3}} = \dfrac{3\sqrt{3}}{\lambda}

λ=9\lambda = 9
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