De M la lon nhat thi 1/(50-x) cung phai lon nhat
suy ra 50-x la nho nhat vay tu do 50-x la so duong nho nhat
50-x=1
x=49
b, De N la nho nhat 4/(x-8)
vay x-8 la lon nhat
x-8 la so nguyen am lon nhat
x-8= -1
x=7
xin loi minh khong go dau vi voi sai thi thoi nhe cau thu lai di