The equation of family of parabola with focus at origin and the X -axis at its axis is, y2‌‌=−4a(x−a) y2‌‌=−4ax+4a2 2yy′‌‌=−4a a‌‌=−‌
yy′
2
Therefore, y2=2yy′(x+‌
yy′
2
) y=2y′(x+‌
yy′
2
) y=2xy′+yy′2y(‌
dy
dx
)2+2x‌
dy
dx
−y=0 Thus m‌‌=‌ order ‌ ‌‌=1 And n‌‌=degree ‌‌=2 Hence, mn−m+n‌‌=2−1+2 ‌‌=3