Let's integrate: <math><mo>∫(</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>)dx</mo></math>
 <math><mfrac><mrow><msup><mrow><mi>x</mi></mrow><mrow><mn>4</mn></mrow></msup></mrow><mrow><mn>4</mn></mrow></mfrac></math>
Indefinite integrals are defined up to an additive constant <m>C</m>, so this yields: <math><mfrac><mrow><msup><mrow><mi>x</mi></mrow><mrow><mn>4</mn></mrow></msup></mrow><mrow><mn>4</mn></mrow></mfrac><mo> + </mo><mi>C</mi></math>

▷<b>Answer: &nbsp; <math><mfrac><mrow><msup><mrow><mi>x</mi></mrow><mrow><mn>4</mn></mrow></msup></mrow><mrow><mn>4</mn></mrow></mfrac><mo> + </mo><mi>C</mi></math></b><span style='font-size:smaller'>, with <m>C</m> being any constant &nbsp; &nbsp; (processing: 3 steps, 2 ms)</span>