a2 - a - 56 = 0 হলে, a এর মান কত?

A 7, - 8

B 8, - 7

C 5, - 6

D 14, - 4

Solution

Correct Answer: Option B

a2 - a - 56 = 0
⇒ a2 - 8a + 7a - 56 = 0
⇒ a(a - 8) + 7(a - 8) = 0
⇒ (a - 8)(a + 7) = 0
হয়, a - 8 = 0
∴ a = 8

অথবা,
a + 7 = 0
∴ a = - 7

∴ নির্ণেয় সমাধান, a = 8, - 7

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