Determining a function given points and slopes

calculusderivativesfunctionspolynomialstangent line

A polynomial function of degree 2 passes through the point P(1, 3). At this point the
function’s slope (i.e. the slope of its tangent) is 1 and at the point Q(2, y) it has a
slope of 5. Determine the function.

I am not sure how to approach this question. I have found the equation for the tangent lines: y = x + 2 and y = 5x – 10 + y for points P and Q respectively. I know that the function will have the general form $𝑓(x) = ax^2 + bx + c$. However, I am not sure how to implement this information in order to find the function. I know I am supposed to use derivatives but not quite sure how.

Best Answer

HINT

Let $P(x) = ax^{2} + bx + c$. According to the given data, we can conclude that

\begin{align*} \begin{cases} P(1) = a + b + c = 3\\\\ P'(1) = 2a + b = 1\\\\ P'(2) = 4a + b = 5 \end{cases} \end{align*}

Can you take it from here?