If y = x² - 3, then the slope of the tangent line at the point (2, 1) is equal to the value of dy/dx when x = 2. We have
y = x² - 3 ==> dy/dx = 2x
so when x = 2, the slope of the tangent is 4.
This tangent passes through the point (2, 1) on the curve, so it has equation
y - 1 = 4(x - 2)
==> y = 4x - 7
