Answer:
18. C (3x -1)(x +8)
19. A (x +1)(x +3)
20. D (3x -2)(x -2)
Step-by-step explanation:
Since you know how to multiply binomials, you can easily check any of the offered answers to see if they work.
(ax +b)(x +c) = ax² +(b+ac)x +bc
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18. All of the constants except for choice D multiply to give -8, so you must check the middle term:
A b+ac = 1-24 = -23 ≠ 23
B b+ac = -8+3 = -5 ≠ 23
C b+ac = -1+24 = 23 . . . . . this is the answer
D already eliminated because bc = 8 ≠ -8
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19. The only answer with constants that multiply to give +3 is A.
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20. The only answer with constants that multiply to give +4 is D.
