The method of Problem 20 can be extended to second order equations with variable coefficients. If y1 is a known nonvanishing sol
ution of y′′ + p(t)y′ + q(t)y = 0, show that a second solution y2 satisfies (y2 /y1 )′ = W (y1 , y2 )/y21 , where W (y1 , y2 ) is the Wronskian of y1 and y2 . Then use Abel’s formula [Eq. (23) of Section 3.2] to determine y2 .
Just by estimating, 54% is a little over 1/2 of 168. You know by that, that neither A or B is close. The real answer is 90.72, so if your instructor wants you to round up, it would be D
