Its intercepts on the x and y axes are a and b respectively.
It is given that
1/a + 1/b = constant = k (assume)
1/ka + 1/kb = 1
According to the given condition :
Hence 1/k, 1/k satisfies equation.
x/a + y/b = 1
Hence the line passes through the fixed point (1/k, 1/k)