По теореме Виета:
х1+х2= -b/a=5/2= 1.5
x1*x2= c/a= -4/2 = -2.
#1
(x2^2+x1^2)/(x1*x2)= (x2^2 + x1^2 + 2x1*x2 - 2x1*x2)/(x1*x2) = ((x1 + x2)^2 - 2x1*x2)/x1*x2= (1.5^2 - 2*(-2))/(-2) = 3.125
#2
x1x2(x1^3+x2^3) = -2* (x1+x2)(x1^2 - x1x2 + x2^2) = -2*1.5*(x1^2 + x2^2 + 2x1*x2 - 2x1*x2 - (-2)) = -3*((x1+x2)^2 - 2x1*x2 + 2) = -3*(1.5^2 + 4 + 2) = -24.75.