Chapter 3: Applications of Differentiation
Section 3.10: Antiderivatives
Example 3.10.1
If fx=3 x2−6x+5, find the antiderivative Fx for which F4=15.
Solution
Mathematical Solution
Like differentiation, antidifferentiation is a linear operator that "goes past" sums and multiplicative constants. Applying the Power rule (Table 3.10.1) to each power of x in the expression for fx=3 x2−6 x1/2+5, the general antiderivative is
Fx=3 x33−6 x3/23/2+5 x+c=x3−4 x3/2+5 x+c
Solve the equation F4=64−32+20+c=15 for c=−37 so that the desired antiderivative is
Fx=x3−4 x3/2+5 x−37
Maple Solutions
The following solution is obtained with the AntiderivativePlot command.
Tools≻Load Package: Student Calculus 1
Loading Student:-Calculus1
Control-drag fx=… Context Panel: Assign Function
fx=3 x2−6x+5→assign as functionf
Apply the AntiderivativePlot command.
Context Panel: Simplify≻Simplify
AntiderivativePlotfx,output=antiderivative,value=4,15
−69+x3−4⁢x3/2+5⁢x+16⁢4
= simplify
−37+x3−4⁢x3/2+5⁢x
Note the value option used in the AntiderivativePlot command. The list of two numbers α,β assigned to this option determine c in the equation Fα=β.
To obtain a solution from first principles, obtain the general antiderivative with the rules in Table 3.10.1 or with the tool in Table 3.10.1(a). Then solve the equation F4=15 for the additive constant c as in the Mathematical Solution above.
fx=
Table 3.10.1(a) A tool for obtaining antiderivatives
Extract the antiderivative from Table 3.10.1(a) via copy/paste.
Select the antiderivative in Table 3.10.1(a)) and copy the expression as per Figure 3.10.1(a)
Figure 3.10.1(a) The copy step
Expression palette: Evaluation template Paste antiderivative (from clipboard) Evaluate at x=4 and set equal to 15 Press the Enter key
Context Panel: Solve≻Solve
x3+5⁢x−4⁢x32+_Cx=a|f(x)x=4=15
84−16⁢4+_C=15
→solve
_C=−69+16⁢4
Expression palette: Evaluation template Paste antiderivative (from clipboard) Reference _C by its equation label Press the enter key.
x3+5⁢x−4⁢x32+_Cx=a|f(x)
x3+5⁢x−4⁢x32−69+16⁢4
−37+x3−4⁢x32+5⁢x
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