3sinα+cosα=0,tanα=-1/3,sin²α+2sinα*cosα-3cos²α=(sin²α+2sinα*cosα-3cos²α)/(sin²α+cos²α)=(tan²α+2tanα-3)/(tan²α+1)=(1/9-2/3-3)/(1/9+1)=-16/5 .