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4 ∫ 1 F ( X ) D X W H E R E F ( X ) = { 7 X + 3 , I F 1 ≤ X ≤ 3 8 X , I F 3 ≤ X ≤ 4 - Mathematics

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Question

\[\int\limits_1^4 f\left( x \right) dx, where f\left( x \right) = \begin{cases}7x + 3 & , & \text{if }1 \leq x \leq 3 \\ 8x & , & \text{if }3 \leq x \leq 4\end{cases}\]

Sum
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Solution

We have,

\[\int\limits_1^4 f\left( x \right) dx, where\ f\left( x \right) = \begin{cases}7x + 3 & , & \text{if }1 \leq x \leq 3 \\ 8x & , & \text{if }3 \leq x \leq 4\end{cases}\]

LaTeX

\[I = \int_1^4 f\left( x \right) d x\]
\[ \Rightarrow I = \int_1^3 f\left( x \right) d x + \int_3^4 f\left( x \right) d x ...................\left[ \text{Additive property} \right]\]
\[ \Rightarrow I = \int_1^3 \left( 7x + 3 \right) d x + \int_3^4 8x d x\]
\[ \Rightarrow I = \left[ \frac{7 x^2}{2} + 3x \right]_1^3 + \left[ 4 x^2 \right]_3^4 \]
\[ \Rightarrow I = \frac{63}{2} + 9 - \frac{7}{2} - 3 + 64 - 36\]
\[ \Rightarrow I = \frac{56}{2} + 34\]
\[ \Rightarrow I = 62\]
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Definite Integrals
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Chapter 20: Definite Integrals - Exercise 20.3 [Page 55]

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RD Sharma Mathematics [English] Class 12
Chapter 20 Definite Integrals
Exercise 20.3 | Q 1.3 | Page 55

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