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3.4c Integration as the Inverse of Differentiation


3.4c Integration as the Inverse of Differentiation

Example:
Shows that  d dx [ 2x+5 x 2 −3 ]= −2( x 2 +5x+3 ) ( x 2 −3 ) 2 Hence, find the value of  ∫ 0 2 ( x 2 +5x+3 ) ( x 2 −3 ) 2  dx


Solution:
d dx [ 2x+5 x 2 −3 ]= ( x 2 −3 )( 2 )−( 2x+5 )( 2x ) ( x 2 −3 ) 2                   = 2 x 2 −6−4 x 2 −10x ( x 2 −3 ) 2                   = −2 x 2 −10x−6 ( x 2 −3 ) 2                   = −2( x 2 +5x+3 ) ( x 2 −3 ) 2 ∫ 0 2 −2( x 2 +5x+3 ) ( x 2 −3 ) 2  dx = [ 2x+5 x 2 −3 ] 0 2 −2 ∫ 0 2 ( x 2 +5x+3 ) ( x 2 −3 ) 2  dx = [ 2x+5 x 2 −3 ] 0 2      ∫ 0 2 ( x 2 +5x+3 ) ( x 2 −3 ) 2  dx =− 1 2 [ ( 2( 2 )+5 2 2 −3 )−( 2( 0 )+5 0 2 −3 ) ]                                  =− 1 2 [ 9−( − 5 3 ) ]                                  =− 1 2 × 32 3                                  =− 16 3                                  =−5 1 3

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