Question

The graph of y = sqrt of x has a normal with equation y = −8x + b, where b is a real constant. Find the value of b.

Answer 1

Differentiate y=sqrt{x} then find the x value for which the gradient is 1/8 (as it's a normal, the products of the gradients will be -1). Plug this x value back into y=sqrt{x} to find the y value, then use these two values to find b.