5) 6(m+3)=(6*m)+(6*3)=6m+18
8)4(b-3)=(4*b)-(4*3)=4b-12
1000×7+(444×7-399×7)-(685×7+353×7)
444×7=3108
399×7=2793
3108-2793=315
685×7=4795
353×7=2471
4795+2471=7266
1000×7=7000
7266+7000=14266
=(sin²α/2-cos²α/2)(sin²α/2+cos²α/2)=-(cos²α/2-sin²α/2)·1=-cosα