Here's the question you clicked on:
cshashishanker
In lect1-Differentiation..while ascertaing the coordinates for Q point x0 and Δx were used for X coordinates but y did he used f(x0+Δx) for Y coordinates inspite of using y0and Δy??
Hi! Δx isn't a literal position, but rather, it's the distance Q is from x0 along the x-axis. This is why Δx, "delta x", is also known as the "change in x". So we know P is at (x0, f(x0)), where f(x0) is also known as y0. The point Q's x-coordinate is Δx distance away from x0, so its x-coordinate is x0+Δx. The point Q is actually at (x0+Δx, f(x0+Δx)). Δy, similarly isn't the y-coordinate of Q, but rather Δy is the distance Q is from P along the y-axis. Δy is "delta y" or the "change in y". Aside from (x0+Δx, f(x0+Δx)) we can also say Q is at (x0+Δx, y0+Δy).