Engineering Board Exam Reviewer · Trigonometric Integrals and Substitution · hard

Evaluate: 1x2 x2 + 9,dx (assume x>0)

  1. x2 + 99 x+C
  2. - x2 + 93 x+C
  3. - x2 + 99 x2+C
  4. - x2 + 99 x+C

Answer

D. - x2 + 99 x+C

Solution

Let x=3 , dx=3 2 ,d , sqrt(x2+9)=3 . Then 3 2 /9 2 ·3 ,d = 19 / 2 ,d =-1/9 +C. Since = xsqrt(x2+9), the result is - sqrt(x2+9)9x+C.

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