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If the coefficients of x 2 and x 3 are both zero, in the expansion of the expression (1 + ax + bx 2 ) (1 – 3x) 15 in powers of x, then the ordered pair (a,b) is equal to :

1. (28, 861)
2. (28, 315)
3. (–21, 714)
4. (–54, 315)

Correct answer: (28, 315)

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