Quadratic function [value range] Given the quadratic function [y = x & sup2; - 4x-3], if - 1 ≤ x ≤ 6, then the value range of Y is_________ .

Quadratic function [value range] Given the quadratic function [y = x & sup2; - 4x-3], if - 1 ≤ x ≤ 6, then the value range of Y is_________ .

From the perspective of image, the parabola opening of the function is replaced by - B / 2a to get the symmetry axis as x = 2, and then the vertex coordinates are (2, - 7), and then the maximum and minimum values are obtained. When x = - 1, y = 2, when x = 6, y = 9. Because the lowest point is - 7 and X decreases from - 1 to 2, and x increases from 2 to 6, it is concluded that - 7 ≤ y ≤ 9 - 7 ≤