The tangent to the curve `2a^(2)y=x^(3)-3ax^(2)` is parallel to the `x` -axis at the points

Find points at which the tangent to the curve y=x^(3)-3x^(2)-9x+7 is parallel to the x-axis.

Point (s) at which the tangent to the curve y=(a^(2)x)/(a^(2)+x^(2)) is parallel to the X - axes is (are)

The tangent to the curve y=ax^2+bx at (2,-8) is parallel to X-axis then

Points at which the tangent to the curve y=x^(2) (x-2)^(2) is parallel to the X- axes are

Find points at which the tangent to the curve y=x^(3)-3x^(2)-9x+7 is parallel to the x-axis