Patrick B. answered 03/07/21
Math and computer tutor/teacher
dy/dx = 4 y / x^2
x^2 dy = 4 y dx
dy/y = 4 dx / x^2
ln y = 4 (-x ^(-1)) +c
y = exp ( -4/x + c)
initiial condition: 1 = exp ( -4/-4 + c)
1 = exp (c + 1)
ln 1 = c+1
c = -1
y = exp ( -4/x - 1)
check:
ln y = -4/x - 1
dy/y = 4/x^2 dx
which is the same as the original D.E
with condition y(−4) = 1.