# Homework Help: Simple Integration question.

1. Aug 16, 2011

### ozone

If one could just explain how the attached answer below was derived I would be greatful. Thanks!

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2. Aug 16, 2011

### sir_manning

By being very careful with your minus signs! What did you try? Remember that 'a' is a constant and you are integrating with respect to 'x'.

3. Aug 16, 2011

### dynamicsolo

The anti-derivative function is $$a^{2}x - \frac{1}{3} x^{3} .$$ You then evaluate it at x = a and x = -a (or at x = a and double the result, since the integrand function is symmetrical about the y-axis [the anti-derivative is zero at x = 0 ] ).