y = -0.1 x² + 4x -11
B(x; y) вершина у = ax²+bx+c
x(B) = -b/2a
x(B) = -4 / -0.2 = 20
y(B) = -0.1 * 400 +80-11 = -40+80-11 = 40-11 = 29
B(20; 29) - вершина параболы
