How do you use Integration by Substitution to find intdx/(5-3x)?

1 Answer
Jul 25, 2014

The answer is

-1/3*ln(5-3x)+c, where c is constant

Solution
For problems like

int dx/(a+bx),

we start with assuming a+bx=u
then, differentiating this assumption b*dx=du

dx=(du)/b

Now, substituting this in problem,

int(du)/(b*u) = 1/b*lnu +c, where c is constant

now, substituting u in the solution,

1/b*ln(a+bx)+c

Similarly following for the problem,
let 5-3x=u
then, -3*dx=du
now substituting in the problem, we get

int-1/3*(du)/u = -1/3*ln(u)+c

Finally, plugging in u, the answer will be -1/3*ln(5-3x)+c