∫(1 + 3x)x² dx

Question image

Understand the Problem

The question is asking us to evaluate the integral of the function (1 + 3x)x². This involves using integration techniques, such as polynomial expansion and then applying the power rule of integration.

Answer

The integral evaluates to $$ \frac{x^{3}}{3} + \frac{3x^{4}}{4} + C $$
Answer for screen readers

The result of the integral is

$$ \frac{x^{3}}{3} + \frac{3x^{4}}{4} + C $$

Steps to Solve

  1. Expand the integrand

First, distribute ( x^2 ) across the terms in the parentheses:

$$ (1 + 3x)x^2 = x^2 + 3x^3 $$

  1. Set up the integral

Now we can rewrite the integral using the expanded form:

$$ \int (x^2 + 3x^3) , dx $$

  1. Apply the power rule of integration

Using the power rule, which states that ( \int x^n , dx = \frac{x^{n+1}}{n+1} + C ), integrate each term:

For ( x^2 ):

$$ \int x^2 , dx = \frac{x^{3}}{3} $$

For ( 3x^3 ):

$$ \int 3x^3 , dx = 3 \cdot \frac{x^{4}}{4} = \frac{3x^{4}}{4} $$

  1. Combine the results

Now combine the results of the integrals:

$$ \int (x^2 + 3x^3) , dx = \frac{x^{3}}{3} + \frac{3x^{4}}{4} + C $$

  1. Simplify if necessary

Sometimes, it might be helpful to express the final answer in a single fraction, but here we leave it as is for clarity.

The result of the integral is

$$ \frac{x^{3}}{3} + \frac{3x^{4}}{4} + C $$

More Information

The process of expanding the integrand and then applying the power rule is a fundamental technique in calculus. It allows you to solve many integrals involving polynomials easily. Remember that ( C ) represents the constant of integration, which is essential in indefinite integrals.

Tips

  • Forgetting to include the constant of integration ( C ).
  • Misapplying the power rule, such as failing to increase the exponent correctly.
  • Ignoring to distribute correctly during the expansion step.

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