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The concept of a primitive

Primitives of common functions

Table of common antiderivatives

Function f Antiderivative F Interval
f(x) = a (constant) F(x) = a*x R
f(x) = x^n (n an integer, n ≥ 1) F(x) = x^(n+1)/(n+1) R
f(x) = 1/x² F(x) = -1/x ]0;+∞[ or ]-∞;0[
f(x) = 1/√x F(x) = 2*√x ]0;+∞[
f(x) = 1/x F(x) = ln(x) ]0;+∞[
f(x) = e^x F(x) = e^x R
f(x) = cos(x) F(x) = sin(x) R
f(x) = sin(x) F(x) = -cos(x) R

Linearity

If F is an antiderivative of f and G is an antiderivative of g, then:

  • F + G is an antiderivative of f + g
  • kF is an antiderivative of kf (where k is real)

Example: an antiderivative of 5x^2 + 3 is 5*(x^3/3) + 3x = (5/3)x^3 + 3x.

Detailed example

Find an antiderivative of f(x) = 4x³ - 2x + 7 on ℝ. We deal with each term: the antiderivative of 4x³ is x⁴, the antiderivative of -2x is -x², and the antiderivative of 7 is 7x. Therefore, F(x) = x⁴ - x² + 7x + C.

Common pitfall

Do not confuse the antiderivative of x^n with its derivative: we ADD 1 to the exponent and DIVIDE by this new exponent (the inverse of the differentiation rule, which multiplies and subtracts 1). Always check by differentiating F to find f.