Let the smaller natural no. be ------>x , then
other natural no. would be -------> (x + 4)
According to the question,
x^2 + (x + 4)^2 = 58
x^2 + (x^2 + 8x + 16) = 58
2x^2 + 8x - 42 = 0
x^2 + 7x - 3x - 21 = 0
x(x + 7) - 3(x + 7) = 0
(x + 7)(x - 3) = 0
now, either (x + 7) = 0 or (x - 3) = 0
if (x + 7) = 0 => x = -7 or if (x - 3) = 0 => 3
x = 3
So, the required numbers are 3 & 7.
