a3 - 21a -20 রাশিটির একটি উৎপাদক হবে নিচের কোনটি?
Solution
Correct Answer: Option C
a3 - 21a -20
= a3 + a2 - a2 - a - 20a - 20
= a2 (a + 1) - a (a + 1) - 20 (a+1)
= (a + 1) (a2 - a - 20)
= (a + 1)(a + 4)(a - 5).
= a3 + a2 - a2 - a - 20a - 20
= a2 (a + 1) - a (a + 1) - 20 (a+1)
= (a + 1) (a2 - a - 20)
= (a + 1)(a + 4)(a - 5).
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