Use a change of variables to evaluate the following indefinite integral. [( Vx + 8) 6 21x dx Determine a change of variables from x to u. Choose the correct answer below. 1 OA. U= 21x OB. U= VX O c. u= (V X +8)6 OD. U= 1X +8 Write the integral in terms of u. ( Vx + 8) 6 21x dx = | () du Evaluate the integral. (Vx + 8) 6 dx = 21x