1. The problem statement, all variables and given/known data Write an equation for the line tangent to the graph of f at x = 1 and use it to approximate f(2.1). 2. Relevant equations y = mx+b f(1) = 4 f'(x) = (3x^2 + 1) / 2y m = 1/2 when x = 1 3. The attempt at a solution Well, if the line is tangent to the graph of f at x = 1, that means they have the same slope (I think). Thus, y = (1/2)x + b I have the point (1, 4) so I plug that in to find b 4 = (1/2)(1) + b b = 8 Thus, I have y = (1/2)x + 8 Since they want me to approximate f(2.1), I would plug in 2.1 for x and solve for y. But, my answer is wrong. The correct answer is y - 4 = (1/2)(x-1) f(1.2) = 4.1 My equation is wrong (and thus my answer), which leads me to believe that I'm approaching this incorrectly.