(a)
If b = -2 the addition of the polynomials = 24x^2 -21x + 15 = the smallest possible polynomial
(d)
2x^2 + 3x + (16 + k)
x^2 - 2x - 5 [ 2x^4 - x^3 + kx^2 -19x -10 ]
2x^4 -4x^3 -10x^2
_________________________________
3x^3 + (10 + k)x^2 -19x
3x^3 -6 x^2 -15x
_______________________________
(16+ k)x^2 - 4x - 10
(16 + k)x^2 - (32 - 2k)x - 80 - 5k
_____________________________
(28 + 2k)x + (70 + 5k)
(28 + 2k) + (70 + 5k) = 0
98 = -7k
-98/7 = -14 = k