N
nhunhungyeuthuong


bai 1: cho he phuong trinh sau ax+by=c
cx+ay=b
bx+cy=a
gia su he tren co nghiem,cmr:a^3+b^3+c^3=3abc
bai 2:goi x,y la nghiem cua he (m-1)x-(m+1)y=3m-2
(m+1)x+(m-1)y=2m
tim GTLN,GTNN cua A=3x+5y-1
cx+ay=b
bx+cy=a
gia su he tren co nghiem,cmr:a^3+b^3+c^3=3abc
bai 2:goi x,y la nghiem cua he (m-1)x-(m+1)y=3m-2
(m+1)x+(m-1)y=2m
tim GTLN,GTNN cua A=3x+5y-1