Question

若|x-y+5|与|x+y-3|互为相反数,求9x-5y的值

Answer 1

|x-y+5|与|x+y-3|互为相反数

|x-y+5|≥0

|x+y-3|≥0

∴x-y+5=0

x+y-3=0

解得

x=-1

y=4

9x-5y=9*(-1)-5*4=-9-20=-29