1) 19+5x>=0 x>=-3.8
2)14+5x>=0 x>=-2,8
3) 2-x-x^2>=0
x^2+x-2<=0
[-2;1]
По теореме Виета
x^2 + px + q = 0
x1 + x2 = - p
x1*x2 = q
x^2 - 16x + 28 = 0
x1 + x2 = 16
x1*x2 = 28