f(x) = x2 + ax + b, then f(x + c) = (x+c)2 + a (x + c) + b = x2 + (2c + a) x + c2 + ac + b which shows that the roots of f (x) are transformed to (x - c) i.e., roots of f (x + c) = 0 are c - c and d - c. Hence, one of the roots of the equation f (x + c) is (d - c).