Find an equation of the tangent line to the parabola y = x - 4x + 5 at the point (1, 2). SOLUTION From the previous example, we know the derivative of f(x) = x - 4x + 5 at the number a is f'(a) = 2a - 4. Therefore the slope of the tangent line at (1, 2) is f'(1) = 2(1) - 4 = Thus an equation of the tangent line, shown in the figure, is y -( ) -(x-([ ]))ory= y = x - 4x+5 2 X Ci