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1.d. If the quadratic x^2+bx-8 factorises as (x+r)(x-s), then r and s must multiply to give -8. As these must be integers, they must be factors of -8.

The pairs of factors that multiply to give -8 are: (x-1)(+8), (x-2)(x+8), (x+1)(x-8) and (x+2)(x-4).

The value of b for each of these pairs is: 7, 2, -7 and -2. Therefore these are the values of b that can produce integer factorisations.