100(87²-13)/(91²-34*91+17²)=(87-13)(87+13)/(91²-2*17*91+17²)=
=74*100/(91-17)²=7400/74²=100/74=50/37.
-15d - 22d² + 10d³ + 33=-15d+10d³-22d²+33=-5d(3-2d²)+11(3-2d²)=(3-2d²)(-5d+11)
X+y = (38,5+12,36)/2 + 3(24,39-16,2)
x+y = 50,86/2 + 3*8,19
x+y = 25,43 + 24,57
x+y = 50,00