For any given ε > 0, we must find a δ > 0 such that
|(2x² - x - 1) - 2| < ε whenever |x - (-1)| = |x + 1| < δ
|(2x² - x - 1) - 2| < ε iff
|2x² - x - 1 - 2| < ε iff
|2x² - x - 3| < ε iff
|(2x-3)(x+1)| < ε
To find the appropriate δ on the interval (-2,0), we know that
|2x-3| < 7
So on the interval (-2,0),
|(2x-3)(x+1)| < ε iff
Thus whenever δ < ε/7, then
|(2x² - x - 1) - 2| < ε
thus
[PROVED]
Edwin