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Use a change of variables to find the following indefinite integral. [ (x+ + x2 ) 12 ( 4x 3 + 2x) dx What is the best choice of u for the change of variables? U= Find du. du = ([dx Rewrite the given integral using this change of variables. [ ( x+ + x 2) 12 ( 4x 3 + 2x) ax = ] ( ) au Find the indefinite integral. J ( x+ + x 2 ) 12 ( 4x 3 + 2x) dx =[