WinApi function graph output

There is a cycle of plotting the function f (x) = x * x * x - 10 * x * x - 3 * x + 59 using LineTo. But when displaying, broken lines are obtained, how can this be corrected?

x, y - coordinates of the center of the screen (500; 250)

kx, ky - scaling factors for x and y, respectively (Scaling when the window is changed)

i * 14 - equalized the width of the chart, without this it draws very narrowly.

for( int i = -10;i <= 10;i++){ LineTo(hdc, x + (i*14)*kx, y - f(i)*ky); }