The tabular method can be applied to any function which is the product of two expressions, where one of the expressions has some nth derivative equal to zero. For instance, the tabular method can be used to find the indefinite integral of x4e3x, but not of sin(x)e3x. This is because the 5th derivative of x4 is equal to zero, whereas sin(x) does not have any nth derivative which always exhibits zero values.
The tabular method uses a convenient table with three columns. We can call the first column “Signs,” the second column “u” and the third column “dv.” Under the column called “Signs,” we list positive and negative signs in alternating order for as many times as the problem requires. The first entry in the column labeled “u” will be the part of the function we want to integrate which can be reduced to zero through successive differentiation. In integrating our sample function, x4e3x, we will put x4 in the column labeled “u.” The subsequent entries in the “u” column will be the successive derivatives of the first entry — all the way to zero.
The first entry in the column labeled “dv” includes the other part of the function we want to integrate. The subsequent entries in this column will be the successive integrals of the first entry. For our sample problem, the first entry in the “dv” column will be e3x.
This is how the table for finding the integral of x4e3x will look:
Using this table to find the indefinite integral of the function requires taking the sign from each row in the column except the last, applying it to the entry for “u” in the same row, and multiplying the result by the entry for “dv” in the next row. Doing this problem on paper, you would simply draw arrows between the following expressions:
+ x4 and (1/3)e3x
– 4x3 and (1/9)e3x
+ 12x2 and (1/27)e3x
– 24x and (1/81)e3x
+ 24 and (1/243)e3x
Now multiply each of the expressions linked by “and” (or the arrows on paper) and add them together to get the final indefinite integral:
(1/3)x4e3x – (4/9)x3e3x + (4/9)x2e3x – (8/27)xe3x + (8/81)e3x + C
Remember to include the constant C if you wish to leave the integral in indefinite form without evaluating it.
The great advantage of using the tabular method is the ability to do integration by parts mechanically, without needing to exert a large amount of thinking about the special circumstances of the problem. The procedure is fairly quick to memorize and easy to retain. After you learn it once, it will always be at your disposal as a tool for quickly and easily determining indefinite integrals that would otherwise take an immense amount of time to find.