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

If $x\phi (x) = \int\limits_5^x {(3{t^2} - 2\phi '(t))dt}$, x > $-$2, and $\phi$(0) = 4, then $\phi$(2) is __________.

Answer (integer) 4

Solution

$x\phi (x) = \int\limits_5^x {3{t^2} - 2\phi '(t)dt}$<br><br>$x\phi (x) = {x^3} - 125 - 2[\phi (x) - \phi (5)]$<br><br>$x\phi (x) = {x^3} - 125 - 2\phi (x) - 2\phi (5)$<br><br>$\phi (0) = 4 \Rightarrow \phi (5) = {{133} \over 2}$<br><br>$\phi (x) = {{{x^3} + 8} \over {x + 2}}$<br><br>$\phi (2) = 4$

About this question

Subject: Mathematics · Chapter: Definite Integration · Topic: Properties of Definite Integrals

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