Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Evaluate ∫ dx/(x2+4x+7).
Options
A <i>(1/√2) tan<sup>-1</sup>((x+3)/√2) + C</i>
B <i>(1/√3) tan<sup>-1</sup>((x+2)/√3) + C</i>
Correct Answer
C <i>(1/√6) tan<sup>-1</sup>((x+7)/√6) + C</i>
D <i>(1/√5) tan<sup>-1</sup>((x+6)/√5) + C</i>
Correct Answer

Option B is the correct answer.

Detailed Explanation

To evaluate this integral, we need to complete the square in the denominator.x2+4x+7 = (x2+4x+4) + 3 = (x+2)2 + 3.So the integral becomes ∫ dx/((x+2)2 + 3).This is in the form of ∫ du/(u2 + a2) = (1/a)tan-1(u/a) + C.Here, u = x+2, so du = dx.And a2 = 3, so a = √3.Substituting these values into the formula:= (1/√3)tan-1((x+2)/√3) + C.This matches option B. (Note: The source document indicates option A was selected, but based on the calculation, option B is correct).

Hint

Complete the square in the denominator to transform the integral into the form ∫ du/(u2 + a2), which integrates to (1/a)tan-1(u/a) + C.

Question Info