Б) (30-1)(30+1) = (30²-1²) = 900-1 = 899
в) (60-1)(60+1) = (60²-1²) = 3600-1 = 3599
г) (100-1)(100+1) = (100²-1²) = 10000 - 1 = 9999
д) (20-2)(20+2) = (20²-2²) = 400-4 = 396
е) (50-2)(50+2) = (50²-2²) = 2500-4 = 2496
<span>-4x+(-3-5x)=30-3x
-4x-3-5x=30-3x
-9x+3x=30+3
-6x=33
x=-11/2
Ответ: x= -11/2 или -5,5</span>
1мин=60сек
20•60=1200(сек)
-31-х=-9
-х=-9+31
-х=22
х=-22