# Function in Maple giving weird plots

In Maple I have defined a function

If I plot within $Q \in [0,100]$ I get

but I get the exact same plot with other boundaries

and if I use $Q \in [0, 10^{-10}]$ I get

How can this happen? What am I doing wrong? I think the last plot is edged because the steps on the y axis is so small that it cannot draw the line as curved as it should be. But I have no idea why the same function can draw the same linear curve ending in different values of $Q$.

The quadratic term is much smaller than the linear term. The closer you look at any curve, by narrowing the range of $x$, the straighter it will look. Instead, try larger ranges of $x$, you will start to see the curve.
For the very narrow range, Maple doesn't store numbers between 44.99999999999997 and 44.99999999999998. This is called round-off error. It happens so rarely that we need the seventeenth decimal place. Also it takes space to store, and time to calculate. I think you can ask Maple to change that precision.

Nothing wrong with the Maple output. The coefficients you provide for the quadratic are miniscule, so for practical purposes, on your indicated range, the function is very close to:

$$PN(Q)=-3.3\cdot 10^{-4}Q+45$$

which is a line of very small slope. To see the quadratic nature of the original, versus the linear approximation, try increasing the desired range:

P := proc (Q) options operator, arrow; 7.4*(1/10000000000)*Q^2+(-1)*3.3*(1/10000)*Q+45 end proc;
PN := proc (Q) options operator, arrow; (-1)*3.3*(1/10000)*Q+45 end proc;


and then:

plot({P(Q), PN(Q)}, Q = -10^6 .. 10^6, color = [red, green]);