`a x^2 + bx + c = 0` has real roots, `a_1 x^2 + b_1 x + c = 0` has real roots, `a,b,c,a_1,b_1,c_1` are real then roots of `(a + a_1)x^2 + (b + b_1)x + (c-c_1 ) = 0 `are