(\(a^2-a\))C2 = (\(a^2\)\(-a\))C4If (a^2 - a)C2 = (a^2 - a)C4, then a

1.	(\(a^2-a\))C2 = (\(a^2\)\(-a\))C4If (a^2 - a)C2 = (a^2 - a)C4, then a =A. 2 B. 3 C. 4 D. none of these
Answer» Option : (B) a² – a = 2 + 4 (ⁿC_x = ⁿC_y ⇒ n = x + y or x = y) a² – a – 6 = 0 a² – 3a – 2a – 6 = 0 a(a – 3) + 2(a – 3) = 0 (a + 2) (a – 3) = 0 a = -2 or a = 3 But, a = -2 is not possible since it’s negative. So, a = 3.

(\(a^2-a\))C2 = (\(a^2\)\(-a\))C4If (a^2 - a)C2 = (a^2 - a)C4, then a =A. 2 B. 3 C. 4 D. none of these

Answer»

Option : (B)

a² – a = 2 + 4

(ⁿC_x = ⁿC_y ⇒ n = x + y or x = y)

a² – a – 6 = 0

a² – 3a – 2a – 6 = 0

a(a – 3) + 2(a – 3) = 0

(a + 2) (a – 3) = 0

a = -2 or a = 3

But,

a = -2 is not possible since it’s negative.

So,

a = 3.