1)13,5*9,1=122,85
2)122,85*(-3,3)=-405,405
3)-405,405:(-0,00013)=3118500
10^-4=0,0001;10^7=10000000;
2,56*0,0001*5,2*10000000=0,000256*52000000=13312.
Прилагаю листочек.......................................
31x + 77 = 15( x^2 + 2x + 1)
31x + 77 = 15x^2 + 30x + 15
- 15x^2 + 31x - 30x + 77 - 15 = 0
- 15x^2 + x + 62 = 0
15x^2 - x - 62 = 0
D = b^2 - 4ac = 1 - 4*15*(-62) = 1 + 3720 = 3721 = 61^2
x1 = ( 1 + 61) / 30 = 62 / 30 = 31 / 15 = 2 целых 1/15
x2 = ( 1 - 61) / 30 = - 60 / 30 = - 2