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Integrals

Antiderivatives by substitution, parts and partial fractions.

Integration undoes differentiation. The solver shows which technique it uses — the power rule, a u-substitution, integration by parts, partial fractions — and the graph plots the antiderivative F against the integrand f, so you can see that F's slope is f.

Kushanda muenzaniso: integral of x*e^x dx

Calculus · Integrals

Integrate x·e^(x)

\int x e^{x}\, dx

Step by step

  1. \int x e^{x}\, dx

    Find an antiderivative.

  2. u = x,\quad dv = e^{x}\, dx

    Integration by parts: ∫u dv = uv − ∫v du.

  3. du = 1\, dx,\quad v = e^{x}

    Differentiate u, integrate dv.

  4. \int x e^{x}\, dx = x e^{x} - \int e^{x}\, dx

    Apply the formula.

  5. \int e^{x}\, dx = e^{x}

    ∫ aᵘ du = aᵘ / ln a (for eˣ that is just eˣ).

  6. = x e^{x} - e^{x}

    Combine.

  7. F(x) = \left(x - 1\right) e^{x} + C

    Add the constant of integration.

Kuratidza mhinduro
\left(x - 1\right) e^{x} + C

Symbols used here

\int f(x)\,dx,\ \int_a^b
integral
Antiderivative (indefinite) or signed area from a to b (definite).
e
Euler's number
2.71828…, the base whose exponential is its own derivative.
\leq,\ \geq
less/greater than or equal
Inequalities that allow equality; < and > exclude it.
\pi
pi
Ratio of a circle's circumference to its diameter, 3.14159…
\infty
infinity
Not a number: "grows without bound" in limits and intervals.
\sin,\ \cos,\ \tan
sine, cosine, tangent
Ratios of sides in a right triangle; coordinates on the unit circle.
\log_b x,\ \ln x
logarithm, natural log
The exponent b must be raised to for x; ln uses base e.
\sum_{k=1}^{n} a_k
summation
Add a_k for k = 1 up to n.
\lim_{x \to a} f(x)
limit
The value f(x) approaches as x approaches a.
f'(x),\ \frac{dy}{dx}
derivative
Instantaneous rate of change; slope of the graph.
y',\ y''
first and second derivative of y
Prime notation for derivatives with respect to x (or t).
C,\ C_1,\ C_2
arbitrary constants
Constants of integration fixed by initial conditions.

How to: Integrals

  1. Find an antiderivative.
  2. Integration by parts: ∫u dv = uv − ∫v du.
  3. Differentiate u, integrate dv.
  4. Apply the formula.
  5. ∫ aᵘ du = aᵘ / ln a (for eˣ that is just eˣ).
  6. Combine.
  7. Add the constant of integration.

Questions people ask

What is a derivative in one sentence?

The slope of the graph at a point — the rate at which the output is changing there. Speed is the derivative of position.

What is an integral in one sentence?

The accumulated total of a rate — the area under the curve. Distance travelled is the integral of speed.

Why are derivatives and integrals opposites?

That is the fundamental theorem of calculus: accumulating a rate and then measuring how fast the accumulation grows gets you back the rate. Integration undoes differentiation up to a constant.

When do I use substitution and when integration by parts?

Substitution when part of the integrand is the derivative of another part (u and du both present). Parts when the integrand is a product of two unrelated kinds of function — a polynomial times an exponential, log or trig function.

Tarisa yako

More in Calculus

LimitsDerivativesDefinite integralsTaylor seriesSeries and sumsMaxima and minimaThe chain ruleImplicit differentiationRelated rates and optimisationIntegration techniques: substitution, parts, partial fractionsApplications of integration: area, volume, arc lengthInfinite series and convergence tests