3x^2-5x-8=0
D=25+4*3*8=25+96=121
x₁=(5+11)/6=8/3
x₂=(5-11)/6=-1
1). 1 1/2 + 2 2/3 = 1 3/6+2 4/6=3 7/6=4 1/6
2) 4 1/6 : 3 3/4 =25/6 : 15/4 = (25* 4) / (6*15)=(5*2) / ( 3*3) = 10/9= 1 1/9
3) 1 1/9 - 2/5 = 1 5/45 - 18/45 = 50/45 -18/45= 32/45
3(x^2-8x+16)-3x^2=3x^2-24x+48-3x^2= -24x+48
1,6 - 1,0 = 0,6
в итоге, значит,на 0,6