Reverse One Rule, Then Check
Borrowed idea: Reverse the rules, then check. Antidifferentiation is differentiation read backwards. The table is the same, and the direction is the only change. Raise the exponent, divide by the new number, and differentiate to confirm. One line of checking beats ten of hoping. The check catches sign errors, exponent errors, and missing reciprocal factors at once, and it costs less time than rereading the work you have just written.
| Exam disguise | What you see on the page | What your brain must translate | Required execution |
|---|
| “Evaluate the integral” with a polynomial | powers and coefficients | reverse power rule | raise, divide, check |
| A rate given as a polynomial | “how many words by the end” | antiderivative then subtract | constant term becomes kx |
| Choices that are functions | four candidate families | differentiate each | pick the one returning the integrand |
| x1 in the integrand | a negative power | the logarithm case | absolute value, plus C |
| A composite like e3x | a linear inner function | reciprocal factor | divide by the inner slope |
① Raise the exponent before doing anything else. Writing the new exponent down first prevents the classic slip of dividing by the old one.
② Handle the constant term separately. A bare number integrates to that number times x, not to zero and not to a higher power.
③ Differentiate the answer. If the result is not the integrand, the error is in the exponent or in a sign, and both are visible in one line.