Hi,
a)
y' + xy^3 = 0
y' = -xy^3
y'/y^3 = -x |Integrate
-1/2*1/y^2 = -1/2*x^2 + c
y^2 = 1/(x^2+c)
y = ±1/√(x^2+c)
b)
-x^2*e^y = y'
-x^2 = y'/e^y |integrieren
-1/3*x^3 + c = -1/e^y |Kehrbruch
e^y = 3/(x^3 + d) |ln
y = ln(3/(x^3+d))
c)
2y' = 3y/x |:2y
y'/y = 3/2*1/x |Integrieren
ln(y) = 3/2*ln(x) + c
y = x^{3/2}*d
Grüße