<br />This new answer is much closer than the original; it is off by about <math>.05</math>. If the number of subintervals is increased, it can be shown that the estimated value approaches the real value:
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<br />This new answer is much closer than the original; it is off by about <math>.05</math>. Note how much less "error" area that there is on the picture. The graph represents the first parabola we use for Example 2 Continued, evaluating from 4 to 6. By reducing the area that each individual parabola approximates, our total approximation became more accurate.
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If the number of subintervals is increased, it can be shown that the estimated value approaches the real value: