And we could do that in point-slope form. We would just have to say y minus the y value that we know is on that line, the point two comma one we know is on that line. So y minus one is going to be equal to the slope of our tangent line, which we know is going to be equal to four, times x minus the x value that corresponds to that y value, so x minus two. So now we just have to substitute x equals 1.9 to get our approximation for f of 1.9. So we'd say y minus one is equal to four times 1.9 minus two. 1.9 minus two is negative 0.1. And let's see, four times negative 0.1, this all simplifies to negative 0.4.