Final answer:
The slope of the line tangent to the graph of f at P is mₜₐₙ = h + 10.
Step-by-step explanation:
To find the slope of the line tangent to the graph of f at P, we can use the formula mₜₐₙ=(f(a+h)-f(a))/{h}.
Given that f(x) = x²-9 and P(-5,16), we can substitute the values into the formula to find the slope.
Substituting the values, we get mₜₐₙ = (f(-5+h) - f(-5))/h = ((-5+h)² - (-5)²)/h = (h² + 10h)/h = h + 10.
Therefore, the slope of the line tangent to the graph of f at P is mₜₐₙ = h + 10.