(3) Differentiating both sides of
with respect to <em>x</em> gives
Solve for d<em>y</em>/d<em>x</em> :
Then the slope of the tangent line to the curve at (1, 9) is
The equation of the tangent line would then be
<em>y</em> - 9 = -2/3 (<em>x</em> - 1) ==> <em>y</em> = -2/3 <em>x</em> + 29/3
(4) The slope of the tangent line to
at a point <em>(x, y)</em> on the curve is
When <em>x</em> = -1, we have a slope of 2/3, so
-(2<em>a</em> + 1)/(-1 - 2)² = 2/3
Solve for <em>a</em> :
-(2<em>a</em> + 1)/9 = 2/3
2<em>a</em> + 1 = -18/3 = -6
2<em>a</em> = -7
<em>a</em> = -7/2