∵
2
3 (x-5 ) 2 +5|m|=0 ,(x-5) 2≥0,|m|≥0,
∴(x-5) 2=0,|m|=0,∴x-5=0,m=0
∴x=5
∵-2a 2b y+1与7b 3a 2是同类项
∴y+1=3,∴y=2
∴2x 2-6y 2+m(xy-9y 2)-(3x 2-3xy+7y 2)
=2x 2-6y 2+mxy-9my 2-3x 2+3xy-7y 2
=-x 2-13y 2-9my 2+mxy+3xy
=-5 2-13×2 2-9×0×2 2+0×5×2+3×5×2
=-47.
∵
2
3 (x-5 ) 2 +5|m|=0 ,(x-5) 2≥0,|m|≥0,
∴(x-5) 2=0,|m|=0,∴x-5=0,m=0
∴x=5
∵-2a 2b y+1与7b 3a 2是同类项
∴y+1=3,∴y=2
∴2x 2-6y 2+m(xy-9y 2)-(3x 2-3xy+7y 2)
=2x 2-6y 2+mxy-9my 2-3x 2+3xy-7y 2
=-x 2-13y 2-9my 2+mxy+3xy
=-5 2-13×2 2-9×0×2 2+0×5×2+3×5×2
=-47.